Raspberry Pi

Miscellaneous

Raspberry pi quick start guide
Learn and make resources from raspberrypi.org.
Lifehacker's Complete Guide to Raspberry Pi
http://elinux.org/RPi_Hub
http://www.raspberrypi-spy.co.uk/
wifi setup

# /etc/network/interfaces  file
auto wlan0
allow-hotplug wlan0
iface wlan0 inet dhcp
allow-hotplug wlan0
  wpa-ssid "YOURSSID"
  wpa-psk "YOURPASSWORD

Berryboot for multiple boots
video player: omxplayer videofile.mp4. See also the Android app OMX Remote (Raspberry Pi).
force sound output from analog
mp3 player: mpg321 "my file.mp3". See https://sites.google.com/site/semilleroadt/home/raspberry-pi about testing sound on Raspberry Pi.
raspberry pi server
re-run configuration
HTG guide to getting started with Raspberry Pi
A month with raspbian and my Beaglebone page about how to fix/change date/time.
My youtube video demostrating GPIO function.
N900 as a remote display
Use Raspberry Pi behind a proxy http://www.raspberrypi.org/phpBB3/viewtopic.php?f=63&t=13986
May 2013 issue of Linux Journal
check current temperatury and cpu freq or this one which contains other RaspPi tricks.

cat /sys/class/thermal/thermal_zone0/temp

This is similar but not the same as the Udoo case where it uses cat /sys/devices/virtual/thermal/thermal_zone0/temp

Play mp3/mp4

use omxplayer. To control volume

omxplayer -o local --vol -2000 Song_Title.mp3  # 10%
omxplayer -o local --vol -602 Song_Title.mp3   # 50%

Get social: connecting with Raspberry Pi

https://www.raspberrypi.org/blog/connecting-raspberry-pi-social/

Why You Should Stop Using a Raspberry Pi for Everything

http://www.makeuseof.com/tag/stop-using-raspberry-pi-everything/

Different generations

https://en.wikipedia.org/wiki/Raspberry_Pi
Raspberry Pi 1 B (512MB memory, released 2012), Raspberry Pi model B vs B+
Raspberry Pi 2 (released 2015. This has an identical form-factor to the existing Raspberry Pi 1 Model B+)
Raspberry Pi Zero WH (released 2017)
Raspberry Pi model 3B (released Feb 29, 2016).
Raspberry Pi model 3B+ (released Mar 28, 2018). Better to use a power adapter with 5V/2.4A or better with 5V/3A. Raspberry Pi 3 Model B vs. 3 B+. Gigabit Ethernet, Dual-band 820.11ac Wi-Fi, Power over Ethernet (PoE).
Raspberry Pi model 4B (released June 24, 2019)

Checking Your Raspberry Pi Revision Number & Board Version

raspberrypi-spy

cat /proc/device-tree/model

Raspberry Pi 4 Rev 1.2. How to tell the difference

https://youtu.be/_wt9NTa1UNE

Displayport connection

Does not work if I use a hdmi to displayport converter. In general, 'step up' is not working but 'step down' is OK. See discussion.

Write image to SD card

Command line. The following tip is from zdnet where -p means to extract files to pipe (stdout). In my case, the status=progress option is not recognized.

unzip -p Image | dd of=/dev/sdX bs=4M iflag=fullblock oflag=direct status=progress

GUI. Etcher.

This is not the end of the process since we cannot use SSH to access Pi. If we follow the instruction to add a 'ssh' to the boot partition, we may get an error SSH problem - Read from socket failed: Connection reset by peer. So it is necessary to hook Pi to a monitor for the first time if we want to access it from SSH.

Create our own image

Make a self-healing raspberry pi: create a recovery partition. The goal is get the machine back to a clean install; particularly in the situation you don’t have access to another device to do the burning.

Prepare your workspace: apt install
Calculate the image size: fdisk
Create the blank image: dd
Partition the image: sfdisk
Mount the images: losetup, partx, dd
Configure and mount partitions: tune2fs, e2label, e2fsck, resize2fs, mount
Set the boot partition: fdisk, nano
Create the reset scripts: chmod, nano
Fix fstab: cat
Take a snapshot: dd, umount, losetup
Burn and test: dd
Physical reset
Raspberry Pi recovery partition code and scripts

Remote access

https://www.raspberrypi.org/documentation/remote-access/access-over-Internet/

Several options are available if you don't want to forward your port, for example, Dataplicity.

Headless Raspberry Pi Setup and SSH access

PS. As of the November 2016 release, Raspbian has the SSH server disabled by default. You will have to enable it manually.

For headless setup, SSH can be enabled by placing a file named 'ssh', without any extension, onto the boot partition of the SD card.

For some reason, I got an error ssh: connect to host raspberrypi.local port 22: Connection refused or “No supported key exchange algorithms. One solution is to generate the keys again Or just wait a little longer for Raspbian to generate keys.

It is also useful to give Pi a new hostname (rpi1, rpi2, rpi3, ...). See Change the Hostname of your Pi.

Change the default password

~~Follow https://www.raspberrypi.org/forums/viewtopic.php?f=91&t=7684, we can ignore checking the password strength (my own simple passwords can not pass when I use the raspi-config utility).~~

If I just use passwd to change the password, the password cannot be too short or simple. However if I use sudo raspi-config, it is fine.

If we like to allow weaker passwords, see here.

$ sudo su -
...
# passwd pi
...
# exit
$

Note it is a good idea to save the password hint as a text file in the HOME directory in case I forget the non-default password. If I forget the password, I can pop out the SD card and insert it into another machine. Then all files can be seen.

Raspbian is not asking for a password for the sudo command

Assign .local domain to Raspberry Pi

Avahi Daemon = Bonjour = Zeroconf = UDP multicast

http://www.howtogeek.com/167190/how-and-why-to-assign-the-.local-domain-to-your-raspberry-pi/

So I can use ssh [email protected] to access RPi.

sudo apt-get update
sudo apt-get install avahi-daemon
# No reboot is necessary for raspberry pi

# from other machines or even Raspi itself
ping raspberrypi.local

The idea was first discovered in Beaglebone.

Get the internal IP address

https://www.raspberrypi.org/documentation/remote-access/ip-address.md

# From another computer
ping raspberrypi.local

# Within raspberry pi
hostname -I

Conky approach

https://www.novaspirit.com/2017/02/23/desktop-widget-raspberry-pi-using-conky/ and my conkyrc.

$ sudo apt-get install conky -y
$ wget -O /home/pi/.conkyrc https://raw.githubusercontent.com/novaspirit/rpi_conky/master/rpi3_conkyrc

I modify .conkyrc file and move NETWORK section to under the 'SYSTEM' section. I also change wlan0 to eth0 since I am using ethernet for connecting to internet.

We can test it by calling conky from the command line (run export DISPLAY=:0.0 if we are calling conky from SSH).

We could make conky running on boot by creating the following two files (+ reboot).

sudo nano /usr/bin/conky.sh

#!/bin/sh
(sleep 4s && conky) &
exit 0

sudo nano /etc/xdg/autostart/conky.desktop

[Desktop Entry]
Name=conky
Type=Application
Exec=sh /usr/bin/conky.sh
Terminal=false
Comment=system monitoring tool.
Categories=Utility;

Note that conky is using 10% CPU (one core) as I see from the htop command. After I remove unnecessary pulling of the system information, it reduces to 4.5% CPU. Another approach is to increase the polling period so that the application is not polling as often.

Note that the top processes shown on conky are not quite correct. The top command gives the top processes. I saw the inconsistency when I import a large database in MySQL.

Set up a static IP address

Setting up Raspberry Pi WiFi with Static IP on Raspbian Stretch Lite. Two files need to be changed.
- /etc/wpa_supplicant/wpa_supplicant.conf - take care of the wifi
- /etc/dhcpcd.conf - take care of a static IP
```
interface wlan0
static ip_address=192.168.1.88
static routers=192.168.1.1
static domain_name_servers=8.8.8.8
```
https://www.raspberrypi.org/learning/networking-lessons/rpi-static-ip-address/ (works on debian stretch). The website is hosted on github. Just need to change /etc/dhcpcd.conf.
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/net_tutorial.md
http://raspberrypi.stackexchange.com/questions/37920/how-do-i-set-up-networking-wifi-static-ip-address (works!)
https://www.raspberrypi.org/forums/viewtopic.php?f=66&t=140252
https://discourse.pi-hole.net/t/how-do-i-set-a-static-ip-address-in-raspbian-jessie-using-etc-dhcpcd-conf/239 or https://www.jeffgeerling.com/blog/2017/setting-pi-hole-whole-home-adtracker-blocking

Under voltage

he red LED going out is an indicator that the supply voltage is too low. You should also see a small coloured square in the top corner of the screen. See the posts

Install minimal browser

http://c-mobberley.com/wordpress/index.php/2013/04/30/raspberry-pi-best-fastest-web-browser-for-gui-usage/

Note that at the end of sudo make install, it will create an item in the menu -> Internet. From the installation output,

sudo install -g dialout web /usr/bin
sudo install -g audio piradio /usr/local/bin
sudo chmod +x /usr/local/bin/piradio
sudo cp ./web.desktop /usr/share/applications
sudo cp ./minimalwebbrowser.png /usr/share/pixmaps
sudo cp ./web.1.gz /usr/share/man/man1
sudo cp ./web-omxplayer.sh /usr/local/bin
sudo chmod +x /usr/local/bin/web-omxplayer.sh

HDMI screen resolution

If the screen size is small (i.e. you can see black margins on 4 sides), uncomment the line about disable_overscan=1.

# sudo nano /boot/config.txt
disable_overscan=1

On my SainSmart 9" monitor, its native resolution 1024x600 is not supported by Raspberry Pi (/boot/config.txt). The resolution becomes 1280x720 if I don't modify anything.

However, there is a workaround on raspberry pi forum. This technique works on Ubuntu-Mate 15 and Raspbian Jessie versions. The two lines (hdmi_group and hdmi_mode) are quite mysterious on Raspbian Jessie but more clear on Ubuntu-Mate.

...
#hdmi_ignore_edid=0xa5000080
hdmi_cvt=1024 600 60 3 0 0 0
hdmi_group=2
hdmi_mode=87
disable_overscan=1

HDMI CEC

Raspberry Pi: Power On / Off A TV Connected Via HDMI-CEC

HDMI monitor/display

Official 7" touchscreen LCD 800x480. Element 14, Official Raspberry Pi 7″ Touch Screen LCD Display assembly guide – install and tips
It works on my Samsung monitor S22C350 (1920x1080).
SainSmart 7" LCD Display Touch Screen TFT Monitor from amazon or from sainsmart.com. 800x480. $39.99 no touch screen, or $49.99 w/ touch screen. Good reviews.
8" IPS LCD Screen with Driver Board Kit for Raspberry Pi$70 frames and support are included!
10.1 inch LCD Display 1366x768 HDMI/VGA/NTSC/PAL there are several issues (poor picture quality, flicker a couple times a second, Overheating, nothing appears on the display) reported in comments.
10" inch TFT LCD Display w/ HDMI+VGA+Video Driver Board for Raspberry Pi
7" TFT LCD Screen Display Monitor for Raspberry Pi B B+ HDMI Board w/ Clear Case
3.5 inch HDMI LCD touchscreen 3.5inch IPS display from waveshare. 480 x 320 (original) or 800x480 (follow their instruction) or DMT mode 9 800x600 60Hz (Raspberry Pi Configuration). For drivers, see
- spotpear.com. I save a copy of the tarball in my github. I use the latest 2019-04-19 Raspbian Stretch. Only the (3.5) HDMI LCD one works for enabling the touch function is sudo ./LCD35-HDMI-800x480-show (Note that using the full path will fail). Other commands such as ./LCD35B-show, ./LCD35B-show-V2 or ./LCD35-show does not work. The webpage said the instruction works for Raspbian/Ubuntu mate/RetroPie but it does not work on Ubuntu mate 18.04.2 (Bionic) (RPi will not be able to start).
- waveshare. The original website. It includes an instruction to calibrate the display. I save the file under my github. The instruction is to 1. unzip 2. cd xinput-calibrator_0.7.5-1_armhf 3. sudo dpkg -i -B xinput-calibrator_0.7.5-1_armhf.deb 4. Click Menu -> Preferences -> Calibrate touchscreen 5. Save the output shown on screen to a file /ect/X11/xorg.conf.d/99-calibration.conf (the directory needs to be created first) according to the screen's instruction. 6. Reboot.
- Power usage (with ethernet): 0.66 (lcd off), 0.86 (lcd on). Raspberry Pi 3 B+ is used here.
- Power usage (without ethernet): 0.56 (lcd off), 0.76 (lcd on), 0.86 (lcd on, wifi on), 1.0 (lcd on, wifi on, chrome)
- Tip of power the pi + LCD by PC USB port: turn off the wifi & unplug the ethernet cable before starting.

Move a Window Without Clicking the Titlebar

Move a Window Without Clicking the Titlebar in Ubuntu. Hold down the Alt key and then click in the window anywhere, and move your mouse.

Use VNC Connect

Raspbian shipped with VNC connect. We can use Android or iOS to connect to the Raspbian desktop.

Make your own screen from an old laptop

See the Hardware page.

Audio output

https://www.raspberrypi.org/documentation/configuration/audio-config.md

Method 1 (works on Raspbian or Ubuntu)

amixer cset numid=3 1

Method 2 (works only on Raspbian)

sudo raspi-config

Select Option 8 Advanced Options and hit Enter, then select Option A6: Audio and hit Enter.

Method 3. Edit /boot/config.txt and setting hdmi_drive variable or hdmi_ignore_edid_audio variable. See the Raspberry Pi config.txt web page.

Capacitive touch vs resistive touch

https://techexplainer.wordpress.com/2012/04/02/resistive-vs-capacitive-touchscreen/

Resistive touch is used in low cost products. It does not support multi-touch.

The official Raspberry Pi DSI touch display & the Kivy library

https://www.raspberrypi.org/blog/the-eagerly-awaited-raspberry-pi-display/. There are two videos demonstrating the (multipoint) touch functionality using Kivy (Python GUI development system) library on the website.
How to build your own smart coffee machine

800×480 display @60fps, 24-bit colour, FT5406 10 point capacitive touchscreen, 70 degree viewing angle, Metal-backed display with mounting holes for the Pi

Adafruit touch screen for Raspi

PiTFT Assembled 320x240 2.8" TFT $35

RCA video output resolution

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=29&t=47527

Hardware acceleration video player

Use omxplayer not VLC. When I use omxplayer to play mp4 videos, htop shows CPUs are not used and the playback is quite smooth. ~~VLC will have a hard time playing the mp4 videos (black screen) not to say all 4 cores are 100% busy on Raspi2.~~ Raspberry Pi software update brings VLC media player with hardware-accelerated video playback

http://elinux.org/Omxplayer
http://kodi.wiki/view/Raspberry_Pi_FAQ
Minimal Kiosk Browser: Kweb - Fast Reliable Web Browser for Raspberry Pi PC.
Linuc command to query video driver

lspci -nnk | grep -i vga -A3 | grep 'in use'

It shows 'nouvea' for my PC Desktop which uses NVIDIA gpu. The command does not work on my Ubuntu-Mate.

pi@pi-ubuntu:~$ lspci -nnk | grep -i vga -A3 | grep 'in use'
pcilib: Cannot open /proc/bus/pci
lspci: Cannot find any working access method.

Memory

When I use 'free -m' or 'htop' command in Raspbian, I see the total memory size only 373MB (Beaglebone black shows 496MB in htop). The reason is Raspbian reserved 128MB for GPU. See

cat /boot/config.txt

Watch youtube with Raspbian

Probably a practical approach is to use 'youtube-dl' program to download the video and then use 'omxplayer' to play it (not streaming anyway).

Auto Startup Application

You can configure what applications should be started at login (NOT at boot time or on start up), in addition to the default startup applications configured on the system.

When I try to add calibre, I see a new file "calibre.desktop" is added to ".config/autostart/" folder.

[Desktop Entry]
Type=Application
Exec=/usr/bin/calibre
Hidden=false
NoDisplay=false
X-GNOME-Autostart-enabled=true
Name[en_US]=Calibre
Name=Calibre
Comment[en_US]=
Comment=

Startup script

http://www.stuffaboutcode.com/2012/06/raspberry-pi-run-program-at-start-up.html. The procedure works for tightvncserver and live-streaming examples. Note that running tightvncserver will use a lot of Raspberry Pi CPU (> 80%).

sudo nano /etc/init.d/NameOfYourScript # Create script in /etc/init.d

sudo chmod 755 /etc/init.d/NameOfYourScript # Make script executable

sudo /etc/init.d/NameOfYourScript start # Test starting the program

sudo /etc/init.d/NameOfYourScript stop # Test stopping the program

# Register your script to be run at start-up and shutdown, run the following command:
sudo update-rc.d NameOfYourScript defaults

# If you ever want to remove the script from start-up, run the following command:
sudo update-rc.d -f  NameOfYourScript remove

Disk Performance

Improving disk performance & the original post.

Power consumption comparison

How long does the RPi last on a battery?

https://raspberrypi.stackexchange.com/a/19825

Bash script to check the RPi status

The script below will check RPi every 60 seconds.

#!/bin/bash
while true
do
  if ping -c 1 192.168.1.11 &> /dev/null
  then
     date
  else
     break
  fi
  sleep 60
done

Ways to power your raspberry pi

10 Ways to Power your Raspberry Pi

Power Raspberry Pi by AA batteries

http://www.raspberrypi-spy.co.uk/2013/04/raspberry-pi-aa-battery-shoot-out/

This also teaches to know how long the battery will die by using Putty and linux command

watch -n 60 uptime

Power by 9V battery

https://youtu.be/h6Bl0Bckl2k You need a regulator (output 1.5V) such as TS7800/TS7805.

Power Raspberry Pi by Lipo batteries

Solar power

Remote water monitoring with a solar powered Raspberry Pi
How-To: Build a Solar Powered Raspberry Pi (video) and materials from adafruit.
Create a portable battery and solar powered Raspberry Pi Zero web server
Solar Powered Weather Station featured MagPi81.

CPU Benchmark

Raspberry Pi 3 (launched 2/29/2016)
Raspberry Pi 2 runs nbench and sysbench by Adafruit.
hackday.com. It includes info about OpenGL benchmark.
http://www.linuxlinks.com/article/20150305172325136/RaspberryPi2-Benchmarks.html

# RPi 1 
pi@raspberrypi:~ $ sysbench --num-threads=1 --test=cpu --cpu-max-prime=20000 --validate run
sysbench 0.4.12:  multi-threaded system evaluation benchmark

Running the test with following options:
Number of threads: 1
Additional request validation enabled.


Doing CPU performance benchmark

Threads started!
Done.

Maximum prime number checked in CPU test: 20000


Test execution summary:
    total time:                          1412.6014s
    total number of events:              10000
    total time taken by event execution: 1412.5301
    per-request statistics:
         min:                                132.41ms
         avg:                                141.25ms
         max:                                403.27ms
         approx.  95 percentile:             172.59ms

Threads fairness:
    events (avg/stddev):           10000.0000/0.00
    execution time (avg/stddev):   1412.5301/0.00

The timing 1412s I got is close to 1318s reported by element14.com.

For nBench, my result of cpu floating-point index 1.753 is also close to element14's 1.884.

pi@raspberrypi:~/nbench-byte-2.2.3 $ ./nbench

BYTEmark* Native Mode Benchmark ver. 2 (10/95)
Index-split by Andrew D. Balsa (11/97)
Linux/Unix* port by Uwe F. Mayer (12/96,11/97)

TEST                : Iterations/sec.  : Old Index   : New Index
                    :                  : Pentium 90* : AMD K6/233*
--------------------:------------------:-------------:------------
NUMERIC SORT        :          202.91  :       5.20  :       1.71
STRING SORT         :          30.842  :      13.78  :       2.13
BITFIELD            :      8.2161e+07  :      14.09  :       2.94
FP EMULATION        :          43.409  :      20.83  :       4.81
FOURIER             :          1660.8  :       1.89  :       1.06
ASSIGNMENT          :          2.2719  :       8.65  :       2.24
IDEA                :          702.86  :      10.75  :       3.19
HUFFMAN             :          421.78  :      11.70  :       3.73
NEURAL NET          :          2.7206  :       4.37  :       1.84
LU DECOMPOSITION    :          73.846  :       3.83  :       2.76
==========================ORIGINAL BYTEMARK RESULTS==========================
INTEGER INDEX       : 11.255
FLOATING-POINT INDEX: 3.161
Baseline (MSDOS*)   : Pentium* 90, 256 KB L2-cache, Watcom* compiler 10.0
==============================LINUX DATA BELOW===============================
CPU                 : ARMv6-compatible processor rev 7 (v6l)
L2 Cache            : 
OS                  : Linux 4.1.13+
C compiler          : gcc version 4.9.2 (Raspbian 4.9.2-10) 
libc                : libc-2.19.so
MEMORY INDEX        : 2.415
INTEGER INDEX       : 3.146
FLOATING-POINT INDEX: 1.753
Baseline (LINUX)    : AMD K6/233*, 512 KB L2-cache, gcc 2.7.2.3, libc-5.4.38
* Trademarks are property of their respective holder.

OpenGL

OpenGL driver for the desktop which uses the GPU to provide hardware acceleration 2/9/2016

Picademy

UPS

http://raspi-ups.appspot.com/en/index.jsp

Books, Magazines, Blogs

Minecraft

Installation

Make sure to use a class 10 (micro)SD card to avoid a hanging problem. This rule applies to other SoC device like Beaglebone and Udoo.

Roll your own Raspberry Pi OS

https://hackaday.com/2018/01/19/roll-your-own-raspberry-pi-os/

Download an image

It is suggested to use torrent to download. In my experience to downloading Raspbian, the number of peers is 50 and the download speed is about 8MB/s.

If we want to use the command line to download the image, we should pay attention to the output file name.

wget --trust-server-names https://downloads.raspberrypi.org/raspbian_latest
# Or
curl -JLO https://downloads.raspberrypi.org/raspbian_lite_latest

The best way of using Raspberry Pi is being able to run multiboot; that is, we have a list of operating systems we can choose to boot.

Raspberry Pi Imager
NOOBS
BerryBoot (just a simple operating system installer, the camera cannot be enabled. The multiple choices of OSs in BerryBoot is now available in NOOBS)

Format a SD card using SD Formatter (Windows & Mac)

http://www.raspberrypi-spy.co.uk/2015/03/how-to-format-pi-sd-cards-using-sd-formatter/

SD Card Speed Test

SD Card Speed Test - Pi Diagnostics

Install an image to a SD card

For example, if I want to install coder, I first download/uncompress the file. Then from the linux command line (assume microSD card is on /dev/sdc)

sudo umount /dev/sdc*
sudo dd bs=4M if=Downloads/coder_v0.4/raspi.img of=/dev/sdc; sync

If I want to watch the progress, I can open another terminal and issue

sudo pkill -USR1 -n -x dd

The output of it still is shown on the 1st terminal where dd is issued. The output looks like

224+0 records in
224+0 records out
939524096 bytes (940 MB) copied, 40.9672 s, 22.9 MB/s
268+0 records in
268+0 records out
1124073472 bytes (1.1 GB) copied, 62.7471 s, 17.9 MB/s

Monitor the progress using pipe viewer

sudo apt-get install pv
dd if=/dev/urandom | pv | dd of=/dev/null

Secure your Raspberry Pi

Wifi setup

A new wifi setup is included in the Raspbian. It is called dhcpcd and dhcpcd-ui. The package name is called 'raspberrypi-net-mods'. PS. the old way is called 'wpa_gui'.

See the blog on May 5, 2015.

USB adapters

I have 3 old USB wifi adapters and they work well in Raspbian. One trick: before I connect the ethernet cable, the wifi was not on for some reason. But once I connect the ethernet cable, it immediately shows SSIDs. This is tested on Pi 2B (it does not include wifi) and Raspbian Buster with desktop (recommended software) released on 2020-02-13.

File:Wifiusb.jpg

Boot from USB

Put /root in USB

How to Run Raspberry Pi 4 or 3 Off an SSD or Flash Drive

Network boot (PXE) w/o microSD

USB network in Pi zero

Mount a USB drive at boot

Add the following line to /etc/fstab (change any values if necessary) and then run sudo mount -a

/dev/sda1 /mnt/share ext4 rw,user,auto 0  0

Also consider to change the mode of the new partition eg sudo chmod 777 /mnt/share.

Pi Desktop

https://www.element14.com/community/docs/DOC-83477

Remote desktop

RealVNC server

Do not download the binary from RealVNC website since it will have a license issue when we want to connect to RPi
VNC Connect and Raspberry Pi
Use the instruction at Github
The current Raspbian includes a vnc server. We need to enable it. No registration is needed when I use my home network. I tested using iOS vnc app.
On linux client side, we can download the binary tar ball and set it executable after untar it.

Connect to Your Raspberry Pi With VNC Connect

Dataplicity

It is not remote desktop but it allows you to access Raspberry Pi from any web browser (no router change, no VPN, no port forward).

To switch to a sudoable account, type su pi. From there you can 'sudo' as normal.

NoMachine

Tips on how to set up your Raspberry Pi for remote access via NoMachine

Web server

How to install a web server on the Raspberry Pi (Apache + PHP + MySQL) Apr 2018

WordPress server

How to Host a WordPress Site on Raspberry Pi

Connection to Raspberry Pi with tightvnc

A simple password like 'raspberry' would work. If we need to reset the password, use vncpasswd command.

# Server side
sudo apt-get install tightvncserver
vncserver
# You will require a password to access your desktops.
# Password: 
# Warning: password truncated to the length of 8.
# Verify:   
# Would you like to enter a view-only password (y/n)? n
#
# New 'X' desktop is raspberrypi:1
#
# Creating default startup script /home/pi/.vnc/xstartup
# Starting applications specified in /home/pi/.vnc/xstartup
# Log file is /home/pi/.vnc/raspberrypi:1.log
ps -ef | grep vnc
# pi        3134     1  0 16:59 pts/0    00:00:00 Xtightvnc :1 -desktop X -auth /home/pi/.Xauthority 
# -geometry 1024x768 -depth 24 -rfbwait 120000 -rfbauth /home/pi/.vnc/passwd -rfbport 5901 -fp 
# /usr/share/fonts/X11/misc/,/usr/share/fonts/X11/Type1/,/usr/share/fonts/X11/75dpi/,/usr/share/fonts/X# 11/100dpi/ -co /etc/X11/rgb
# pi        3217  2666  0 17:01 pts/0    00:00:00 grep --color=auto tightvnc

vncserver             # This line seems not necessary
vncserver –kill :1

# Client side; the most common mistake is to forget to add the port number to the IP address.
sudo apt-get install xtightvncviewer
xtightvncviewer 10.42.0.37:1
# It does not work if I just use raspberrypi.local:1 as the address

To start the tightvnc automatically when boot up, check out http://www.penguintutor.com/linux/tightvnc or my note on BBB.

Also note if the server uses '/usr/bin/vncserver :0', then the client uses 'xtightvncviewer 10.42.0.37'. But if the server uses '/usr/bin/vncserver :1', the client should uses 'xtightvncviewer 10.42.0.37:1', etc. Got the idea!

Note that to troubleshoot the message "GDBus Error:org freedesktop.PolicyKit1 Error.Failed; An Authentication agent already exixts for the given subject", follow the instruction at this message.

Connection from Raspberry Pi to Ubuntu

Follow the instruction and install xtightvncviewer using sudo apt-get and it works. To run the vnc client, just type 'xtightvncviewer' on the terminal.

Another instruction of using tightvnc is at http://www.penguintutor.com/linux/tightvnc.

I have successfully to follow the instruction at http://www.hiddentao.com/archives/2013/09/17/setting-up-tightvnc-on-ubuntu-12-04/ to connect to Ubuntu 12.04 (Unity desktop) from Xubuntu. After launching the following line in my local machine

ssh -L 5901:localhost:5901 [email protected]

I open another terminal window and type the following in my local machine

xtightvncviewer localhost:5901

the Ubuntu desktop appears on my local machine.

Connection from Raspberry Pi to Windows (RDP) with freerdp or rdesktop

The idea is to use Raspberry Pi as a thin client. For example, I can open two remote desktop connections to two separate Windows VMs and the RPi is still quite free in terms of its resource.

Method 1 Use xfreerdp program. Use Ctrl+Alt+Enter to toggle between full and regular screen. Non-full-screen-mode is useful if we want to monitor the RPi resource usage while we are using the remote desktop connection.

1. Open a root terminal. Run
apt-get update
apt-get install freerdp
2. Open a regular terminal. Run
xfreerdp -u brb -x l -z 192.168.1.4

Method 2 We can also use rdesktop program. rdesktop is a free, open source client for Microsoft's proprietary RDP protocol. See wiki.archlinux.org for more tips and tricks about rdesktop.

1. Open a root terminal and run
apt-get update
apt-get install rdesktop
2. Open a regular terminal and run (-f means full screen. Or we can use -g 1280x700 to specify the display resolution)
rdesktop -f -u brb 192.168.1.4

Method 3 There is also an interesting project called RPi-TC/Raspberry Pi Thin Client project. I have not tried it yet.

Raspbian

Directly Connect to a Raspberry Pi Without Internet

http://www.makeuseof.com/tag/directly-connect-raspberry-pi-without-internet/

Recovery partition

Make a self-healing raspberry pi: create a recovery partition

Working from home with your Raspberry Pi

https://www.raspberrypi.org/blog/working-from-home-with-your-raspberry-pi/. Set up email, Office, Google Drive, VPN client, Google hangout (video conference), Skype, VPN Connect.

Raspbian desktop for PC

Download it from here.

Tested Debian Stretch version (2019-4-11) on Virtualbox. It can be installed as either 32-bit or 64-bit OS (uname -m).

Raspbian repository and mirrors

https://www.raspberrypi.org/downloads/raspbian/
http://www.raspbian.org/RaspbianMirrors
UMD mirror (http|rsync)://mirror.umd.edu/raspbian/raspbian

Releases lists

Raspbian package repository URL

http://archive.raspbian.org/raspbian/pool/main/r/r-base/

Sending an email on boot

See the wiki page - Email IP On Boot.

The python code works interactively when I use in in a command line. But it does not work when I use it in /etc/rc.local nor /boot/boot.rc.
The cron method works for my case (wifi connection); see looking at it the cron job is more reliable, placing it in the rc.local file fails on wifi.

@reboot sleep 300 && python /home/pi/startup_mailer.py

Make sure the gmail account is set up to be "less secure"; see Login credentials not working with Gmail SMTP. Is it possible to use salted password?
How to Send Emails with Gmail using Python

Fix Dirty COW

https://www.raspberrypi.org/blog/fix-dirty-cow-raspberry-pi/ (10/25/2016)

Kernel building

Create a custom kernel using Vagrant

Adafruit Pi Kernel-o-Matic

Emulate Raspbian on Linux/Windows

http://xecdesign.com/qemu-emulating-raspberry-pi-the-easy-way/

Emulate Intel X86 on raspberry Pi (ARM)

https://eltechs.com/product/exagear-desktop/ (non-free)

Digital clock format

Right click task bar -> Panel Settings -> Panel applets -> Digital clock -> Preferences -> "%r %a %D" (default is %R). This will give something like "08:19:11 PM Sun 01/21/18".

Browser

GNOME Web/Epiphany browser

This is the default in Raspbian Jessie.

Some annoying thing is the browser is using the DuckDuckGo as the search engine which is not configurable.

Some web pages cannot be shown correctly (see my comment in LuaKit)

LuaKit - an extremely lightweight browser based on webkit and GTK+

This is very cool. It solves the issue of using Web to open http://magazine.odroid.com. It even supports Adobe Flash (eg some videos from Amazon.com)

sudo apt-get install luakit

Mastering keybinds is the key to use it (Even a mouse cannot be used to close a Tab).

Some examples:

j/k to scroll down/up
space or ctrl+d / Ctrl+u to scroll down/up one page
h/l to scroll left/right
+/- to zoom in/out.
(ctrl + o) OR (shift + h) to go to the previous page. Ctrl + i to go forward.
forward slash (/) to search within the page. Use n to find the next occurrance, N to find the previous one.
B for bookmark
gB to show bookmarks
gH to go to home page
: command mode
Esc normal mode
t open webpage in new tab
d delete current tab
:print print page

We can modify the key bindings. I run

sudo nano /etc/xdg/luakit/binds.lua

and on line 321 about "Go back in the browser history" (search the keyword 'history'): change "H" to "b". Now I can hit the lowercase 'b' button to go back to a previous web page instead of Shift+h.

    key({}, "b", "Go back in the browser history `[count=1]` items.",
        function (w, m) w:back(m.count) end),

Iceweasel browser

This browser looks like a clone of Firefox (firefox is not available in the repository). The version in Raspbian Jessie is 38.4.0. If iceweasel is not installed (e.g. jessie 8.0), we can install it by

sudo  apt-get install iceweasel --no-install-recommends

Firefox browser

See Iceweasel above. Firefox package has been replaced by Iceweasel so it is not available via apt-get install.

Vivaldi browser

http://www.makeuseof.com/tag/vivaldi-best-browser-raspberry-pi/

Chinese input

sudo apt-get install fcitx fcitx-chewing

Reboot and the task bar will show an icon to let you switch the language. Tested on Raspberry jessie 8.0.

Raspbian uses PIXEL desktop, a modified LXDE desktop environment.

We need to add chewing to the input method. See this postfor a detailed instruction.

Bluetooth keyboard

The GUI program blueman does not work on the pairing step (it does not accept my entered keys) for my bluetooth keyboard (my bluetooth mouse works).

My working example is to use the command line way (bluetoothctl). The bluetoothctl utility is part of the bluez package I think. Raspbian Jessie does not have the bluez-utils package). See https://wiki.archlinux.org/index.php/Bluetooth

# Press the 'connect' button on the bluetooth keyboard first!
$ bluetoothctl # no sudo is needed
[bluetooth] default-agent
[bluetooth] scan on
[bluetooth] pair 90:7F:61:8F:D0:38        # it will ask to enter a pin code
[bluetooth] connect 90:7F:61:8F:D0:38

It is also interesting to see bluetooth related programs under /usr/bin directory. Those programs shown on my Raspbian are quite different from the ones shown on my Ubuntu 14.04.

New Bluetooth GUI in Raspbian

https://www.raspberrypi.org/blog/another-update-raspbian/ (May 13, 2016). This should solve the problem mentioned above though I haven't tried it.

Text editor

Why Coding for Raspberry Pi Is Way Better With Code-OSS, a community compiled version of VS Code, on the Raspberry Pi.

Pi zero

Getting Started with the Raspberry Pi Zero W (mini HDMI) without a Monitor

https://www.losant.com/blog/getting-started-with-the-raspberry-pi-zero-w-without-a-monitor (Raspbian Stretch)

Turn Raspberry Pi Zero into a USB gadget

http://blog.gbaman.info/?p=791 (this can only work with the RPi Zero). Allowing ssh, sftp, vnc etc over a single usb cable.
Pi Zero USB OTG. GPIO Zero is installed by default in the Raspbian image
Connect To A Raspberry Pi Zero With A USB Cable And SSH. The same procedure works on Pi Zero W. Still there is no internet on my zero W unless we create wpa_supplicant.conf under /boot. In summary, we need to modify 2 files and create 1 file.
- config.txt
- cmdline.txt
- wpa_supplicant.conf
- ssh

# Stretch lite
pi@raspberrypi:~ $ free -m
              total        used        free      shared  buff/cache   available
Mem:            433          23         336           3          73         359
Swap:            99           0          99

Run sudo raspi-config and sudo apt update after we connect RasPi.

On Mac, I can immediately connect to raspberry pi zero by using ssh [email protected]. However, on Ubuntu, I cannot. The solution is simple. Open the network setting, choose "Ethernet Coneected" > "Wired connection 2" and click "IPv4". Choose "Link-Local Only" instead of the default "Automatic (DHCP)". Then click the "Apply" button.

Add USB type A to Raspberry Pi zero

Raspberry Pi Zero with USB socket Type-A expand (solder)

Top 10 Raspberry Pi Zero Projects That Make Use of Its Small Stature

http://lifehacker.com/top-10-raspberry-pi-zero-projects-that-make-use-of-its-1792403310

OpenElec

I use NOOBS to install OpenElec with Raspbian.

Still there is no a regular web browser. Not a joke. Remember OpenElec is installed in multiboot mode through NOOBS. Probably a better approach is to consider Arch-Linux.

There is a program called 'Web viewer'. Wonder when would it be useful.

Need to change 2 settings in order to get date & time correctly.

Another installation method is to download/install the image directly from the OpenELEC website. See

Email server

Host your own email with projectx/os and a Raspberry Pi

SMS server

https://www.howtoforge.com/tutorial/how-to-install-raspberry-pi-sms-server/

Kodi black screen when exit

A temporary solution is use Ctrl + Alt + F2 then Ctrl + Alt + F1. See

https://www.raspberrypi.org/forums/viewtopic.php?t=91111&p=637126.
https://gist.github.com/aperezm-vlex/75d7481afff0db8f5894 A script to fix this problem. Some people have issues.
https://www.raspberrypi.org/forums/viewtopic.php?t=139758&p=926771. Create a new file by sudo nano /usr/local/bin/startkodi. chmod +x and put the following.

    #!/bin/bash
    fbset_bin=`which fbset`
    xset_bin=`which xset`
    xrefresh_bin=`which xrefresh`
    if [ ! -z $fbset_bin ]; then
      DEPTH2=`$fbset_bin | head -3 | tail -1 | cut -d " " -f 10`
    fi
    kodi "$@"
    if [ ! -z $fbset_bin ]; then
      if [ "$DEPTH2" == "8" ]; then
        DEPTH1=16
      else
        DEPTH1=8
      fi
      $fbset_bin -depth $DEPTH1 > /dev/null 2>&1
      $fbset_bin -depth $DEPTH2 > /dev/null 2>&1
    fi
    if [ ! -z $xset_bin ] && [ ! -z $xrefresh_bin ]; then
      if [ -z $DISPLAY ]; then
        DISPLAY=":0"
      fi

      $xset_bin -display $DISPLAY -q > /dev/null 2>&1
        if [ "$?" == "0" ]; then
          $xrefresh_bin -display $DISPLAY > /dev/null 2>&1
        fi
    fi
    VT="$(fgconsole)"
    if [ "$VT" ]; then
      sudo chvt 7
      sudo chvt "$VT"
    fi

and a simpler solution

#!/bin/bash
kodi
if [ "$?" = "0" ]; then
killall kodi
fbset -depth 8 && fbset -depth 16
xrefresh
fi

Corebird - twitter client

https://mig5.net/content/installing-corebird-debian-jessie

We also need automake, autoconf, autogen, intltool packages.

Unfortunately running ./autogen.sh --prefix=/usr gets stuck at the error message 'configure error: valac >= 0.28.0 is required'. At this moment, valac has a version 0.26. See https://packages.debian.org/jessie/valac.

Backup Raspbian

https://www.raspberrypi.org/documentation/linux/filesystem/backup.md

# Backup
sudo dd bs=4M if=/dev/sdb | gzip > raspbian.img.gz
# Restore
gunzip --stdout raspbian.img.gz | sudo dd bs=4M of=/dev/sdb

SD Card Copier

Raspbian Menu > Accessories > SD Card Copier. It works. The SD card size can be smaller than the original one as long as it has a larger size than the current "/dev/root" partition. After the microSD card has been used once by SD Card Copier, then it can not be used again by the utility (the SD card is labelled in Copy to Device option but it's greyed out. Note even the File Manager cannot mount it in Raspbian but Ubuntu still can auto mount the microSD card). Why? When I insert a ext4-formatted USB drive, the SD Card Copier can use it.

piclone

https://github.com/raspberrypi-ui/piclone

PiShrink

How to transfer a Raspbian image from a 16GB MicroSD card to an 8GB SD card

Backup server

https://opensource.com/life/16/3/turn-your-old-raspberry-pi-automatic-backup-server using rdiff-backup utility.

USB over ip

Its mainuse is to let you access data on USB drives stored on other hardware.

Top 10 Apps You Should Install on Your Raspberry Pi

NAS

Create a hardened Raspberry Pi NAS Dec 2016
- It includes installing Docker and installing an nginx web server.
- It also use software RAID-1 with two hard drives for redundancy.
- Samba
- NFS: unencrypted but gives higher level of performance than Samba between Linux/UNIX hosts. Can be mounted over the network to appear as a local directory
- SFTP
- Backup using rsync
Building a network attached storage device with a Raspberry Pi 2018.
- Series 1. fdisk, autofs, NFS
- Series 2 Automating (incremental) backups on a Raspberry Pi NAS. It has a shell script to list yearly, monthly, weekly and daily backups.
- Series 3 Host your own cloud with Raspberry Pi NAS
Create a NAS with your Raspberry Pi and Samba

OpenMediaVault

lynda.com

NextCloudPi

https://ownyourbits.com/nextcloudpi/

DNS server

Pi-hole

https://twitter.com/The_Pi_Hole
https://github.com/pi-hole/ and https://github.com/pi-hole/pi-hole
http://pi.hole/admin
Create a Network-Wide Ad Blocker with a Raspberry Pi
Pi Hole Ad Blocker with Pi Zero W (and PiOLED)
Setting up a Pi Hole for whole-home ad/tracker blocking (Raspbian)
How to change DNS server on your Android phone or tablet
Pi hole prevent ads from appearing on Internet-connected devices that aren't a Web browser. Pi-hole can be installed on hardware that's not a Raspberry Pi.
Installing pi-hole on ubuntu 18.04 LTS
How to block mobile ads with Raspberry Pi and Pi-hole
Use Web Interface to log in and use Whitelist to allow an access to some domains.

One way to test it is to open the Android app 'Taiwan Radio' or 'FainTV'. You will see the ads cannot be loaded anymore. In fact, this also fixed the buffering problem when I use the 'Taiwan Radio' app.

Install on Pi

No 'sudo'
Uncheck to install lighttpd since I have apache installed already

curl -sSL https://install.pi-hole.net | bash

I am using wifi and it works fine
At the end it will say the install log is in /etc/pihole
The web interface is at http://pi.hole/admin or http://192.168.x.x/admin. The Admin Webpage login password will be shown on the text UI and the terminal too (remember to save it).
The pi-hole admin password can be reset by pihole -a -p
Ports 53 and 80 need to be opened. sudo netstat -tulpn | grep LISTEN
To change the interface from eth0 to wlan0, use pihole -r to reconfigure. see Change ip adress
My current pi-hole version is v4.4 (2020-04), AdminLTE v4.3.3 and FTL v4.3.1. pihole -v It also shows what is the latest versions.
On my Dasung non-ereader tablet (Android 8.1.0) it does not have DNS option on WiFi network. I install DNSPipe. It seems to work. It does ask something related VPN, why?

Update

$ pihole -up

After I upgrade to 5.0, the stats on the dashboard is not working. A solution is here. sudo apt install php7.0-sqlite and sudo service apache2 restart. Use php -v to check your PHP version before confirming the exact module name to install.

Uninstall

$ pihole uninstall
....
  [i] The following dependencies may have been added by the Pi-hole install:
    dhcpcd5 git iproute2 whiptail cron curl dnsutils iputils-ping lsof netcat psmisc sudo unzip wget idn2 sqlite3 libcap2-bin dns-root-data libcap2 lighttpd php7.0-common php7.0-cgi php7.0-sqlite3 php7.0-xml php-intl 
  [?] Do you wish to go through each dependency for removal? (Choosing No will leave all dependencies installed) [Y/n] n
  [✓] Removed Web Interface
  [✓] Removed /etc/cron.d/pihole
  [✓] Removed lighttpd configs
  [✓] Removed config files
  [✓] Removed pihole-FTL
  [✓] Removed pihole man page
  [✓] Removed 'pihole' user
...

VPN

How to run your own OpenVPN server on a Raspberry PI

IPV6 connectivity

https://raspberrypi.stackexchange.com/questions/37/ipv6-connectivity

There are no hardware limitations for IPv6 connectivity, only software must support it. On Arch distribution, IPv6 is enabled by default, so if you have a router with DHCPv6 or RA, you will automatically get connected to the IPv6 internet.

Raspbian supports IPv6, but the kernel module is not loaded by default (which is a crying shame in the wake of recent developments). IPv6 can be enabled at run time by modprobe ipv6 command or at boot time by appending ipv6 to /etc/modules.

Connect your dumb printer to your home network

Raspberry Pi Print Server: Setup a Network Printer. The steps are

Installing the Raspberry Pi Print Server Software (Cups)
Setting up SAMBA for the Pi Print Server (Samba)
Adding a printer to CUPS
Adding a Raspberry Pi Print Server to Windows

Done!

Another instruction How to set up a print server on a Raspberry Pi

6 Ways to Print With a Raspberry Pi

NagiosPi: Turn Your Raspberry Pi into a Network Monitoring Tool

https://www.makeuseof.com/tag/turn-raspberry-pi-network-monitoring-tool/

Embedded Linux

What I Wish I’d Known When I Was an Embedded Linux Newbie from Linux Journal.

How to Install Windows Software on Raspberry Pi Using Wine

https://www.makeuseof.com/tag/install-windows-software-raspberry-pi/

Virtualization

Virtualizing a Raspberry Pi with QEMU

Rpi-Monitor: monitor a Linux system

Monitor/manage multiple raspberry pis

Monitoring Multiple Pis With Nagios (Raspberry Pi)

Use a systemd unit/service file to control an application to start when Raspberry pi boots up

Systemd Essentials: Working with Services, Units, and the Journal

# Start the service
sudo systemctl start nginx.service
# Stop the service
sudo systemctl stop nginx.service
# Restart the service
sudo systemctl restart nginx.service
# Reload the service
sudo systemctl reload nginx.service

# Enable a service to start automatically at boot
sudo systemctl enable nginx.service
# Disable the service again
sudo systemctl disable nginx.service

# List all active unit files
systemctl
systemctl | grep epaper.service 
# Note: ps -ef won't detect epaper.service

# List all the units installed on the system
systemctl list-unit-files

See Raspberry PI 3 E-paper 2.7 inch Clock and Weather Display example from E-ink section.
Configure Docker to start on boot

Install node.js

Install Node.js and Npm on Raspberry Pi

Share your keyboard and mouse between computers with Barrier

Mate Ubuntu

The desktop looks good. But it does not include Mathematica software nor Arduino. It does include Scratch, Sonic Pi (under Programming) and Minecraft Pi (under Games).

After Raspi2 is on for several days with Firefox browser use, the memory is getting lost even Firefox is closed. top command shows /usr/sbin/irqbalance ate 48% memory. It works when I use sudo kill -9 to stop the process. See some discussions at askubuntu.com set ENABLED=0 in /etc/default/irqbalance.

The system looks very stable. See my screenshots below.

Ubuntu-mate 16.04 on Rpi 3B+

16.04.2 image 2017 Feb. The problem is the old image would not boot on (new) Rpi 3B+.
How to enable support for Raspberry Pi 3B+ and 3A+ in Ubuntu MATE
16.04.2 Won’t boot on RPi 3 Model B+
Set Up and Upgrade Ubuntu MATE 16.04 on a Pi 2/3/3B+

SSH server

The website said the server is not installed by default. To install it, run sudo apt install openssh-server

To start it at startup,

sudo systemctl enable ssh.service

Change to use static IP

Use GUI network manager

Install more screensaver themes

http://greyblake.com/blog/2013/02/02/install-more-screensavers-on-mate-desktop/

Take a look at the .desktop files under /usr/share/applications/screensavers.

Web browser

Ubuntu-Mate includes Firefox. I can feel FF is more slow than the browser in Raspbian.

Printer

(Update 12/11/2016): the instruction below using PPD file still has a problem when I print pdf files. The instruction here solves the problem. The idea is to download the official Linux driver (<linux-brprinter-installer-2.1.1-1.gz>) from brother website HL-5250DN.

When I try to add a new Printer (network printer, Brother HL-5250DN) through automatic detected method, I got an error "server-error-internal-error". When I looked at the /var/log/cups/error_log file, it showed "empty PPD file". The following two pages are helpful.

https://bugs.launchpad.net/ubuntu/+source/system-config-printer/+bug/254202
http://www.openprinting.org/printer/Brother/Brother-HL-5250DN (PPD file). A copy of the ppd file (a text file) is saved on github.

The manual approach mentioned in bugs.launchpad.net (#6) works.

System -> Adminstration -> Printers -> Add
Enter URI and specify ipp://192.168.1.88:631/ipp as the Device URI (the address is obtained through the nmap command and look for port 631)
Check the 2nd option 'Provide PPD file' instead of the 1st one 'Select printer from database'.
Browse the location of the PPD file
Continue the procedure until the end. We can print a test page to make sure the setup is successful.

The printer test page said the driver is BR5250_2.PPD and version 1.03.

PS. About the technology terms

Kodi

After I used apt-get to install Kodi, Kodi will not be able to launch:( On Raspbian, the Kodi installed by apt-get works!!!

Best Raspberry Pi Operating Systems for Various Purposes

Arch Linux

Kodi can be installed in ArchLinux by installing the kodi-rbp package. See wiki.archlinux.org.

Android

Assuming you have Raspi 2 and 3.

RaspAnd($9), currently it is Android 7.1.1. See RaspAnd brings Android 7.1.1 Nougat to your Raspberry Pi
Android TV Nougat ROM now available for Raspberry Pi 3
How to Install Android on a Raspberry Pi Apr 10, 2018
How to Build an Android TV Box With a Raspberry Pi (LineageOS 15.1 (Android 8.1.0)) July 03, 2019
How to Install Android (Emteria) on Raspberry Pi (Raspberry Pi 3 Model B) Jan 25, 2020
- How to Setup Android 7 for the Raspberry Pi (EmteriaOS) including GApps.

pi-top

I pledged pi-topCEED ($99 + shipping is $25). The hardware looks cool: 14 inch, 1366x768 resolution (like an old laptop) & a GPIO card that helps to connect 3 wires from pi-top hub to Raspberry Pi. One problem is after connecting the wires from pi-top hub to Raspberry Pi, there is not enough space for me to slide in the cover.

Unfortunately the pi-top OS is unstable (tested 7/1/2016).

first try - screen flicked & is frozen
I download the image (homepage -> Community -> FAQ) and write it to the sd card - works great but after another boot the screen appeared and then disappeared.

I found when I connect the wires of 3-pins with a wrong direction, Raspi still works (pi-top OS & Raspbian). It seems only the 5v and gnd pins are needed.

For some reason, after I shut down the computer the back light is still on. The software from rricharz in github can let Rasbpian users to change the brightness of the screen and also power off the pi-top (bright light off). The original post is on the pi-top forum with the subject 'Using standard Raspbian Jessie on pi-top'.

40-pin connector vs jumper cables. We can use Google account to join.

The current pi-topCEED webpage
Detect and configure pi-top hubs and accessories on Github

Some pictures (left: Pi-top, middle: pi-top hub, right: raspberry pi 3 with a GPIO card). The pin numbers are sequential.

Cable 1: connect to pins 4 (red to 5v) & 6 (black to GND).
Cable 2: connect to pins 19, 21 & 23 (3 holes face down). All are SPI pins.
Cable 3: connect to pin 26. SPI pin.

Backlight: When the display goes to blank, the backlight is still on. With Pi-Top Sirius OS, it (see the Github page) provides a python command to turn the backlight off. The problem is this has to be done manually (pt-brightness --backlight 0 ). And after we did it manually we are unable to see the screen; so it is difficult to interact with the system ? (simple experiment: pt-brightness --backlight 0; sleep 15; pt-brightness --backlight 1 )

Maybe it is possible to add a button/switch to launch a command for controlling the backlight.

Using a push button with Raspberry Pi GPIO. This works after we change the callback function. Step 1. Run the script ‘’python push_button.py’’, step 2. Run ‘’pt-brightness —backlight 0’’ when we want to turn off the backlight 3. Press the button when we want to turn back the backlight.

import os
def button_callback(channel)
    os.system(‘date; pt-brightness —backlight 1’)

pi-topOS

It is based on LXDE but the desktop looks very modern (thumbs up). It is based on the latest Raspbian (Buster).

I feels the theme is like Pop!_OS. Very clean and good icon/font size on pi-topCeed.

Plex

How to Turn a Raspberry Pi into a Cheap Plex Player with RasPlex
How to Turn a Raspberry Pi Into a Plex Media Server
How to Turn a Raspberry Pi into a Plex Server. Just about every Plex player supports MKV without transcoding on the fly.

DVR

How to build a cheap cord-cutting DVR using Raspberry Pi

Kodi/XBMC and OpenElec

Install Kodi on Raspbian
For some reason, I did not find 'Display Mode' option in the System > Settings > System > Video Output in the OpenElec. When I install Kodi (14.2 Mar 27 2015) in Ubuntu 14.04, I can see this option.

Then OpenElec from NOOB works fine.

How to fix Youtube daily limit exceeded

https://kodihome.blogspot.com/

How to Set Up a Kodi Remote Control

https://www.makeuseof.com/tag/set-up-kodi-remote-control/

7 Essential Kodi Tips for New Users

http://www.makeuseof.com/tag/essential-kodi-tips-new-users/

12 Ways to Make Kodi the Best Media Player for You

http://www.makeuseof.com/tag/make-kodi-best-media-player/

The 12 Best Kodi Add-Ons for Watching Live News

https://www.makeuseof.com/tag/best-kodi-add-ons-live-news/

What is OpenElec

Unlike other Kodi solutions, OpenELEC is not based on Ubuntu. In fact, it's not based on any Linux distribution; OpenELEC has been built from scratch specifically to act as a media center. That means it doesn't include drivers for things that just won't be used like 3G cards and graphics tablets, for example.

OpenELEC, however, only includes software required to run Kodi. Because of that it is tiny (roughly 150MB), it installs literally in minutes, and, it can boot extremely quickly in 5-20 seconds, depending on the hardware type used.

In addition, OpenELEC is designed to be managed as an appliance: it can automatically update itself and can be managed entirely from within the graphical interface. Even though it runs on Linux, you will never need to see a management console, command terminal or have Linux knowledge to use it.

Default folders for OpenElec

OpenELEC:~ # ls
backup       emulators    music        screenshots  videos
downloads    lost+found   pictures     tvshows
OpenELEC:~ # df -h
Filesystem                Size      Used Available Use% Mounted on
devtmpfs                165.2M         0    165.2M   0% /dev
/dev/mmcblk0p5          159.8M    103.7M     56.1M  65% /flash
/dev/mmcblk0p6           13.3G    706.6M     11.9G   5% /storage
/dev/loop0               93.9M     93.9M         0 100% /
tmpfs                   170.2M         0    170.2M   0% /dev/shm
tmpfs                   170.2M      4.6M    165.6M   3% /run
tmpfs                   170.2M         0    170.2M   0% /sys/fs/cgroup
tmpfs                   170.2M      4.0K    170.2M   0% /tmp
tmpfs                   170.2M    412.0K    169.8M   0% /var
/dev/mmcblk0p1          820.2M    744.4M     75.8M  91% /var/media/RECOVERY
/dev/mmcblk0p3           27.0M      1.2M     23.5M   5% /var/media/SETTINGS

Youtube plugin error

How to Fix Kodi’s YouTube “Quota Exceeded” Problem

How to Cast YouTube and Other Web Videos to Kodi (Like the Chromecast)

No sound

http://forum.kodi.tv/showthread.php?tid=130371

Click on the Volume icon and raise the volume from the default -60dB to a higher value.

Fix date/time in OpenElec

http://www.htpcbeginner.com/fix-openelec-incorrect-time-raspberry-pi/

Note the original post does not work on the current Kodi 14.1. The utility /usr/sbin/ntpdate is not found. Search the keyword 'daCaPo says' on the above webpage and following his answer does solve the problem. nano /storage/.config/autostart.sh and add the following

#!/bin/sh
(sleep 30; \
/sbin/ntpd -p pool.ntp.org; \
)&

Then chmod +x /storage/.config/autostart.sh. No need to reboot.

UPnP

When I enable the UPnP server function in Kodi, the Kodi can be found in the UPnp client program eg VLC (desktop), BubleUPnP, BSPlayer, Kodi, ....

The Kodi server will be seen to have Music Library and Video Library. The files in Video Library are the same as what I have in the Kodi but the Music Library does not have any songs (it only has Categories like Genres, Artists, Albums, Songs, Years, Top 100, Recently added albums, Recently played albums). According to this Kodi's wiki page: Your audio files MUST have a valid ID tag for them to work properly in the Kodi music library. . Probably it is for this reason, the songs do not appear in the UPnP client software (except the BSPlayer which can find all my songs in the music directory, but BSPlayer does not show my image files in the pictures directory. Such a pity!)

Display Chinese characters

http://forum.kodi.tv/showthread.php?tid=81081

Go to System - Settings - Appearance - Font and choose 'Arial'.

Add-ons

The USTV VoD and Navi-X and USTVNow (require US citizen & registration, free NBC, CBS, ABC, CW, FOX & PBS channels) work well. Just download the zip files in the linux and install them from xbmc -> system -> add ons -> install from local zip files.

Power Up Your XBMC Installation with These Awesome Add-Ons
How to Make XBMC Easier to Use (Especially for Non-Geeks)
Keyboard shortcut. For example, backslash \ for toggle full-screen and windowed mode.
xbmchub maintenance and fix buffering problem.
5 Best Live TV Addons For Kodi
TVADDONS - A Collection of Unofficial Addons for Kodi.
How to install Exodus for Kodi
Youtube Youtube addon included in Kodi is marked for deletion. Use this link to download the zip file (5.1.20.1) install the new it.

Take a screenshot

ssh and run

kodi-send --action="TakeScreenshot"

A new file <screenshot000.png> will be saved under screenshots folder.

LXDE (same as Lubuntu) X11 desktop environment used by Raspbian OS

Inside .config/lxpanel is a directory with the name of your current lxsession profile - and inside this is a further subdirectory called panels.Each file in this directory is the definition of a single panel. See Magpi33.pdf.

Screenshots

https://www.flickr.com/photos/xmodulo/sets/ and Raspbian specific.

Taking a screenshot

scrot

Quick launch bar

To add lxterminal to quick launch bar,

Right click any empty space on taskbar
-> Panel Setting
-> Panel Preferences
-> Panel Applets
-> Application launch bar & Edit
-> Accessories & lxterminal

We can use the same procedure to add Midori to the quick launch bar.

Keyboard shortcut

The shortcuts are defined in the file ~/.config/openbox/lxde-rc.xml

For example,

open the lxpanelctl menu, click Ctrl + ESC.
open launch an application, click Windows + r.
Toggle full screen, Alt + F11.
Launch task manager, Ctrl + Alt + Del.

Get internet by sharing the internet from another machine

https://wiki.archlinux.org/index.php/Internet_Share
static iP. Set up host eth0 IP and then set up RPi IP:
- In Windows, allow Internet sharing. An IP of 192.168.0.2 will be automatically assigned to the Laptop's network card. Make static IP of 192.168.0.2 in Rasp Pi. Enter subnet mask and gateway (192.168.0.1). Also make an entry in /etc/resolv.conf with nameserver=192.168.0.1. Reboot and Rasp Pi will get Net all right.
- In Linux, An IP of 10.42.0.37 will be assigned to eth0 card. Make static IP of 10.42.0.37 in Rasp Pi. Enter subset mask and gateway (10.42.0.1). Also make an entry in /etc/resolv.conf with nameserver=10.42.0.1. Reboot and Rasp Pi will get Net all right.
- Other thoughts:

sudo nano /etc/network/interfaces

iface eth0 inet static
address 192.168.100.1
netmask 255.255.255.0
network 192.168.100.0
broadcast 192.168.100.255
gateway 192.168.100.254

The gateway is important and in most cases will always point to your firewalls, switch or routers IP address.

In my current setting, the host machine's eth0 has IP 10.42.0.1 (inet addr). The RPi has IP 10.42.0.37 and gateway 10.42.0.1.

$ netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         192.168.1.1     0.0.0.0         UG        0 0          0 wlan0
10.42.0.0       0.0.0.0         255.255.255.0   U         0 0          0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U         0 0          0 wlan0
192.168.1.0     0.0.0.0         255.255.255.0   U         0 0          0 wlan0

And /etc/resolv.conf may be worth to be changed too. /etc/hostname and /etc/hosts are unnecessary.

An example of /etc/resolv.conf (set up linux DNS) shown from my RPi is

nameserver 10.42.0.1

But maybe another choice is nameserver 8.8.8.8.

Some tools for discovering the IPs in a network include Fing (iOS/Android) or Scapy (python).

Get internet from mobile tethering

https://github.com/InitialState/rpi-gps/wiki/10%20Part%203.%20Mobile%20Data

IP scan tools

arp (fastest, installed by default)

arp -a 
arp -a -i eth1      # if eth1 comes from a USB ethernet adapter

nmap command
fing (ios, android, linux, windows). Command line usage

sudo fing -n 192.168.1.1/24

where /24 means 'network prefix' size 24 bits. Check wikipedia classless inter domain routing. For example, CIDR notation 192.168.100.0/24 would be equivalent to 192.168.100.0/255.255.255.0.

Angry ip scanner cross platform. open source. It shows all instead of found ip's.
netbios. It does not discover linux boxes, however.

Use Raspberry Pi as a Tunnel Gateway/Router

Build a 10 USD Raspberry Pi Tunnel Gateway

Clustering

Five years of Raspberry Pi clusters 2020. The Docker load-balanced LED cluster Raspberry Pi is interesting!

with 2 Pis

This Linux Journal article teaches how to run GlusterFS Server on two Raspberry Pis. This is also called redundant filesystem. So if one Pi is down, the other keeps the system up.

4 Pis

http://makezine.com/projects/build-a-compact-4-node-raspberry-pi-cluster/. It also shows how to display IP on 1 4pins 16x2 LCD (worked for Arduino & Raspberry Pi). No fancy software were installed to make the cluster.

Hadoop

Qt on Raspberry Pi

Check out https://qt-project.org/wiki/Qt-RaspberryPi

Native build Qt

http://qt-project.org/wiki/Native_Build_of_Qt5_on_a_Raspberry_Pi

Qt-Creator

Ubuntu Snappy

Some more information about ubuntu snappy (username/password is ubuntu/ubuntu):

Suppose I connect my Raspberry Pi 2 get its internet through my computer's USB-ethernet adapter. Then once RPi 2 is on, I can open my browser on my host PC and go to http://webdm.local:4200/. It shows

Note that the SNAPPY UBUNTU CORE image for RPi seems buggy. For example,

ubuntu@localhost:~$ sudo su
root@localhost:/home/ubuntu# dpkg-reconfigure tzdata
cp: cannot create regular file '/etc/localtime.dpkg-new': Read-only file system

Current default time zone: 'America/New_York'
Local time is now:      Thu Jan  1 01:01:42 UTC 1970.
Universal Time is now:  Thu Jan  1 01:01:42 UTC 1970.

debconf: DbDriver "config": could not write /var/cache/debconf/config.dat-new: Read-only file system

root@localhost:/home/ubuntu# snappy info
release: ubuntu-core/devel
frameworks: webdm
apps: 
root@localhost:/home/ubuntu# snappy versions
Traceback (most recent call last):
  File "/usr/bin/snappy", line 25, in <module>
    status = Main().__main__()
  File "/usr/lib/python3/dist-packages/snappy/main.py", line 195, in __main__
    return callback(args)
  File "/usr/lib/python3/dist-packages/snappy/main.py", line 334, in _do_versions
    click_versions = ClickDataSource().versions(all)
  File "/usr/lib/python3/dist-packages/snappy/click.py", line 189, in versions
    all_updates_list = repo.get_upgradable()
  File "/usr/lib/python3/dist-packages/click/repository.py", line 183, in get_upgradable
    headers={"content-type": "application/json"})
  File "/usr/lib/python3/dist-packages/click/network.py", line 70, in http_request
    curl.perform()
pycurl.error: (60, 'server certificate verification failed. CAfile: /etc/ssl/certs/ca-certificates.crt CRLfile: none')

Docker

Docker swarm

Databases

How to set up a Postgres database on a Raspberry Pi

Coding

https://code.org/

Scratch

THE SCRATCH OLYMPICS

Connect Arduino to Raspberry Pi

The Arduino, while not a full-fledged computer, has a few things it does better, like converting analog-to-digital with its built-in ADC chip. How to Use Raspberry Pi and Arduino Together
See doctormonk.com where python-serial module is used and /dev/ttyACM0 is the serial port or the name for the USB interface to the Arduino Uno.
Serial port programming
https://learn.adafruit.com/arduino-lesson-17-email-sending-movement-detector?view=all (closer to Arduino than Raspi). See this internal link. The idea is 1. use Arduino will use PIR to sense any movement. If it detects motion, it will print a string to the serial port 2. the python program has an infinite loop that reads the serial port. If the serial port contains a string starts with the 'M' letter, it will send out an email. So the communication here is one way.

openFrameworks (oF)

openFrameworks is an open source C++ toolkit designed to assist the creative process by providing a simple and intuitive framework for experimentation.

GPIO experiments

RPi.GPIO & gpiozero python libraries

https://www.raspberrypi.org/magpi-issues/Essentials_GPIOZero_v1.pdf#page=10

from RPi import GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
GPIO.setup(4, GPIO.IN, GPIO.PUD_UP)
while GPIO.input(4):
    pass
print("Button pushed!")

from gpiozero import Button
btn = Button(4)
while not btn.is_pressed:
    pass
print("Button pushed!")

Processing

https://www.raspberrypi.org/blog/now-available-for-download-processing/

Power off and on

http://raspi.tv/2012/making-a-reset-switch-for-your-rev-2-raspberry-pi

When we use a diy wire to connect two holes, it will shutdown the RPi immediately. If we disconnect the 2 holes, it will power on the RPi again. I tested it on my Model B running the OpenElec OS. COOL:)

For model B+/Pi 2 model B, see this post. This post also provides another way (GPIO pins 5&6) to shut down RPi.

This has pictures for all raspi models.

How to Add a Power Button to Your Raspberry Pi, lynda.com.

Power from GPIO pins

Pi-top
Powering the Raspberry Pi A+
USB 5V FTDI CP2102 Serial Adapter

Connect to console using TTL/Serial cable

I purchased the TTL cable through dealextream.com. The RaspPi is power by the microUSB (Or we can use the 5V pin on TTL module to connect to 5V on RaspPi. If I try to use 3.3V pin on TTL module to connect to either 3.3V or 5V on RaspPi, it does not work). The connection is done by

   RaspPi    TTL
   =========
   5V          5V
   GND       GND
   TX (14)   RX
   RX (15)   TX

Note that it takes 45 seconds for the screen to respond when I tested it using Putty. The ACT and PWR lights should be on. The tuturial on adafruit is helpful.

C libraries

GPIO layout

40 pins https://pinout.xyz/
26 pins www.raspberrypi-spy.co.uk ,
26 pins raspi.tv
Printable:
- Printable PDF pin layout from here (Colored, lots in one page)
- Another one from here (Good detail, B/W)
- https://mikaelleven.files.wordpress.com/2015/11/rpi_b_gpio_card_mikael-leven.pdf (Colored, only 1)
- https://www.computerhilfen.de/info/wp-content/uploads/2016/04/computerhilfen_de-gpio-pdf-2.pdf (Cool)

Node-RED

lynda.com

WebIOPi

WebIOPi is a REST framework and a webapp which allows you to control Raspberry Pi's GPIO. It does not require apache to be installed. So we can use web browser from Android to control the GPIO in Raspbery Pi ... Another choice is Web.py.

Run Python using webiopi module

sudo python -m webiopi 8000

Start/stop the background service

sudo /etc/init.d/webiopi start
sudo /etc/init.d/webiopi end

Start webiopi at startup:

sudo update-rc.d webiopi defaults

Note that we shall browse to http://localhost:8000/ instead of http://localhost:8000/webiopi. If something is still wrong, use a different port. The default user is "webiopi" and password is "raspberry".

It seems the code is still not stable. I kept getting a message "Error response" Error code 404. Message: Not Found. Error code explanation: 404 = Nothing matches the given URI.

Web.py

http://webpy.org/

See the article The Python Pit - drive your Raspberry Pi with a mobile phone in http://www.themagpi.com/en/issue/9.

Circuit and Electronics

電路與電子學
Circuits and Electronics by MIT

Blink a single LED

I follow the instruction in https://projects.drogon.net/raspberry-pi/gpio-examples/tux-crossing/gpio-examples-1-a-single-led/ to install gpio program/library in raspberry pi. Here is the result

without PI cobbler: check out my video Raspberry Pi + single LED success.
with PI cobbler: see the picture below. The soldering part is not easy for a beginner. Be sure to follow some instruction on youtube videos to begin with. Note that the white stripe is on the edge closest to the SD card.

Another example by using C++ code. No extra library needs to be installed. http://hertaville.com/2012/11/18/introduction-to-accessing-the-raspberry-pis-gpio-in-c/. The site also shows the program to create the diagram is from http://www.fritzing.org.

Python approach. Here it is assumed pin 9 (or 6) is used for GND and pin 11 for GPIO17 (see the GPIO layout above). The LED was connected using a 330 ohm resistor in series with pin 9 (or 6) and 11 to limit the current. Note use “sudo” to run the python code.

import RPi.GPIO as GPIO  
import time  
# blinking function  
def blink(pin):  
        GPIO.output(pin,GPIO.HIGH)  
        time.sleep(1)  
        GPIO.output(pin,GPIO.LOW)  
        time.sleep(1)  
        return  
# to use Raspberry Pi board pin numbers  
GPIO.setmode(GPIO.BOARD)  
# set up GPIO output channel  
GPIO.setup(11, GPIO.OUT)  
# blink GPIO17 50 times  
for i in range(0,50):  
        blink(11)  
GPIO.cleanup()

LED test by gpiozero library.
Google: raspberry pi python led

RGB

http://www.instructables.com/id/Using-a-RPi-to-Control-an-RGB-LED/?ALLSTEPS

16x2 LCD

http://learn.adafruit.com/drive-a-16x2-lcd-directly-with-a-raspberry-pi. The '16x2' LCD means it can show 16 characters per row and there are 2 rows in total. Each character consists of 8x5 (height x width) dots.

http://makezine.com/projects/build-a-compact-4-node-raspberry-pi-cluster/ also tells how to show the IP on the LCD.

8x8 Matrix LED Backpack (I2C)

http://learn.adafruit.com/matrix-7-segment-led-backpack-with-the-raspberry-pi/overview

Another more versatile output from the 8x8 matrix is by using C program. See Mark Williams blog.

I also create a version of launching LED using R. See my youtube video. <youtube>TwoWrPp6_iw</youtube>

Weather Matrix Display

IR Remote with XBMC

http://learn.adafruit.com/using-an-ir-remote-with-a-raspberry-pi-media-center

Stepper motor

Sound sensor

Set up a sound sensor with the Raspberry Pi

I modify the code by

adding a counter in the code for my own interest. See this post for declaring a variable as global.
adding a timestamp to show when an event happened

Note I am connect OUT pin of the sensor to BCM26 on my pi zero.

If I install tmux on my pi zero, I can run the python code, disconnect ssh and connect to it again to see how many time a sound has been detected.

#!/usr/bin/python
import RPi.GPIO as GPIO
import time
import datetime

#GPIO SETUP
channel = 26
GPIO.setmode(GPIO.BCM)
GPIO.setup(channel, GPIO.IN)
counter = 0

def callback(channel):
        global counter
        if GPIO.input(channel):
                counter += 1
                print("Sound Detected! {0} {1}".format(counter,datetime.datetime.now()))
        else:
                counter += 1
                print("Sound Detected! {0} {1}".format(counter,datetime.datetime.now()))

GPIO.add_event_detect(channel, GPIO.BOTH, bouncetime=300) 
GPIO.add_event_callback(channel, callback) 

# infinite loop
while True:
        time.sleep(1)

KOOKYE Smart Home Sensor Kit

CamJam Edukit 3 Robotics Kit

http://raspi.tv/2015/camjam-edukit-3-robotics-kit

Ryanteck Budget Robotics Kit

https://www.indiegogo.com/projects/ryanteck-budget-robotics-kit-for-raspberry-pi

The software control is based on Spacebrew

HummingBird robot

http://www.hummingbirdkit.com/learning/tutorials/raspberry-pi

Add a push button

https://learn.adafruit.com/playing-sounds-and-using-buttons-with-raspberry-pi?view=all Play sound
https://sanje2v.wordpress.com/2014/02/16/adding-shutdownrestart-pushbutton-for-raspberry-pi/ shutdown
https://embeddedcode.wordpress.com/2013/10/18/adding-a-shutdown-button-to-the-raspberry-pi/ shutdown
http://www.raspberry-pi-geek.com/Archive/2013/01/Adding-an-On-Off-switch-to-your-Raspberry-Pi shutdown switch
http://www.instructables.com/id/Raspberry-Pi-Internet-Monitor/?ALLSTEPS Internet monitor with a shutdown switch

Speech synthesis and a push button

https://learn.adafruit.com/speech-synthesis-on-the-raspberry-pi?view=all

Festival speech package

sudo apt-get install festival
# Add voice file
sudo apt-get install festvox-rablpc16k # British English
sudo apt-get install festvox-kallpc16k # American English

Speaking

echo "Hello World!" | festival --tts

wget http://history.eserver.org/jefferson-inaugural.txt
festival --tts jefferson-inaugural.txt

Speak Easier: Flite

sudo apt-get install flite

flite -t "All good men come to the aid of the rebellion"
flite -f jefferson-inaugural.txt

flite -lv
flite -voice awb -t "The Raspberry Pi is a great Maker platform!"

Fun Uses for Speech

sudo apt-get install fortune-mod
fortune | flite

Wav output

flite -t "Shall we play a game?" -o wargames1.wav
aplay wargames1.wav

Reading the Weather

sudo apt-get install weather-util
weather washington
weather -q fips1600190345 | flite

Playing sounds using push buttons (Python).

Use a Simple Button to Control LED

http://raspi.tv/2013/rpi-gpio-basics-6-using-inputs-and-outputs-together-with-rpi-gpio-pull-ups-and-pull-downs

The following site has some elaboration about 'pull down' of resistors. http://www.cl.cam.ac.uk/projects/raspberrypi/tutorials/robot/buttons_and_switches/

Get a Flashing Meeting Reminder with a Raspberry Pi

http://makezine.com/projects/get-a-flashing-meeting-reminder-with-a-raspberry-pi/

Using a servo motor, PWM

LED dimming using software PWM (pulse-width modulation)

http://raspi.tv/2013/how-to-use-soft-pwm-in-rpi-gpio-pt-2-led-dimming-and-motor-speed-control

Reading analog input using external ADC (analog to digital converter) MCP3008

http://learn.adafruit.com/reading-a-analog-in-and-controlling-audio-volume-with-the-raspberry-pi/overview

Reading temperature

https://learn.adafruit.com/adafruits-raspberry-pi-lesson-11-ds18b20-temperature-sensing?view=all

Raspberry Pi has no ADC (Analog to Digital Converter), it cannot directly use an analog temperature sensor like the TMP36.

http://www.cyberciti.biz/faq/linux-find-out-raspberry-pi-gpu-and-arm-cpu-temperature-command/

# GPU
/opt/vc/bin/vcgencmd measure_temp

# CPU
cpu=$(</sys/class/thermal/thermal_zone0/temp)
echo "$((cpu/1000)) c"

and putting them together

#!/bin/bash
# Script: my-pi-temp.sh
# Purpose: Display the ARM CPU and GPU  temperature of Raspberry Pi 2/3 
# Author: Vivek Gite <www.cyberciti.biz> under GPL v2.x+
# -------------------------------------------------------
cpu=$(</sys/class/thermal/thermal_zone0/temp)
echo "$(date) @ $(hostname)"
echo "-------------------------------------------"
echo "GPU => $(/opt/vc/bin/vcgencmd measure_temp)"
echo "CPU => $((cpu/1000))'C"

For my Raspberry Pi 3, the temperature is 52C when it is idle. The temperature can go up to 84C when I build R 3.3.1.

For Pi Zero W, the temperature is 59C when I build R.

MCP23017 GPIO expander (extra 16 pins)

Serial Peripheral interface (SPI)

Camera

# Still image 2592 x 1944
raspistill -vf -hf -o cam.jpg # -vf and -hf is to fix upside-down
gpicview cam.jpg # View the image

# Video 
raspivid -o myvid.h264 -t 60000   
# 60 seconds. Default is 6 seconds which generates 10MB for 1080p, 6.4MB for 720p.
raspivid -o myvid.h264 -t 60000 -vf -hf # fix upside-down
raspivid -o myvid.h264 -w 1280 -h 720   # 1280 x 720 instead of 1920 x 1080
raspivid -o myvid.h264 -w 1280 -h 720 -rot 180 # rotation 180 degree
raspivid -o myvid.h264 -w 1280 -h 720 -b 8000000  
# “8000000” is a bitrate of 8000Kbs (kilo bits per second) or 8Mb (8 mega bits per second). 
# The default is usually 17000000.

# convert h264 to mp4
sudo apt-get install -y gpac
MP4Box -fps 30 -add myvid.h264 myvid.mp4

# play the video
omxplayer myvid.h264
Omxplayer —-win 0,0,800,640 myvid.h264
omxplayer myvid.mp4

http://elinux.org/Rpi_Camera_Module. There are several Android apps to control the camera (Pi or USB) on Raspberry Pi. For example, RaspiCam Remote.
NoIR http://www.raspberrypi.org/learning/infrared-bird-box/
Motion Guide
Surveillance camera by codeproject.com. The same one is also hosted on instructables.com.
http://www.home-automation-community.com/surveillance-with-raspberry-pi-noir-camera-howto/ (take care of user 'motion').

sudo usermod -a -G motion pi
sudo chown motion:motion /home/pi/images
sudo service motion start

To rotate the image, change 'rotate 0' to 'rotate 180' by sudo nano /etc/motion.conf (still not right).

http://pingbin.com/2012/12/raspberry-pi-web-cam-server-motion/ (regular webcam is used)
A post from opsactive.com. Similar to the above.
Turn a Raspberry Pi into a CCTV Security System from averagemanvsraspberrypi.com.
Raspberry Pi CCTV with netcat and mplayer, Netcat (nc) Command with Examples

Connect camera module

Raspberry Pi, the blue part (non-metal) on the cable faces the ethernet port.
On camera module, the blue (non-metal) part is on the same side as the white plastic holder.
The above rule applies to Pi zero W too. That is, the non-metal part faces up and the metal part faces down.

How to connect Raspberry Pi camera module to Raspberry Pi Zero W and the official case

Just Enough Raspberry Pi. The book/site include pictures of different versions of Raspi with large size (cool!). For Raspi Zero W, it shows v1.1 whose camera connector is smaller than a regular Raspi. The camera cable included in pi zero case is a must (one side is regular size and the other side is smaller).

I also find my camera connector is broken when I try to tighten it. Just slide a piece of thick paper will solve the problem; see here.

USB camera

https://www.raspberrypi.org/documentation/usage/webcams/. It says the quality and configurability of the camera module is highly superior to a standard USB webcam.
```
sudo apt-get install fswebcam
fswebcam -r 1280x720 image2.jpg
```
Streaming H264 with Logitech C920

Fisheye Cam

160° Fish Eye

Dash Cam

Create a button-operated camera

https://www.raspberrypi.org/magpi-issues/MagPi45.pdf p27

RPi Cam (Live stream and Cam Web Interface)

http://elinux.org/RPi-Cam-Web-Interface as used in portable streaming camera

The installation is quite simple and the basic installation just works (1/21/2017) with my Pi Camera v2. By default, I can access the live stream by visiting http://raspberrypi.local/html/. The web interface allows me to change camera settings (eg flip image), record video, record image, timelapse, etc. Quite amazing. The first screenshot shows one text dialog during installation and the 2nd screenshot shows the web interface. By default, the live stream will be auto-start. It can be installed on Raspbian-Lite too.

sudo apt-get update
sudo apt-get dist-upgrade

git clone https://github.com/silvanmelchior/RPi_Cam_Web_Interface.git
cd RPi_Cam_Web_Interface
chmod u+x *.sh
./install.sh

How to Use Raspberry Pi as a PC Webcam

Motion triggered infrared wildlife camera, night version camera

Solar powered nature camera

Baby monitor

https://www.raspberrypi.org/blog/raspberry-pi-baby-monitor/

Tiddlybot

https://www.kickstarter.com/projects/1320310506/tiddlybot-fun-and-simple-raspberry-pi-robot/comments
https://www.shopstarter.com/s/Tiddlybot/
http://www.pibot.org/tiddlybot/
https://github.com/Agilic-Development
https://github.com/discoverycode/discoverybot_api The Discovery Bot
http://www.pibot.org/tiddlybot/images/ V1.1 image download link
http://pibot.org/forum/index.php Forum
Two recommended wifi adapters: Edimax EW-7811Un, and the TP link TL-WN725N
http://pibot.org/forum/index.php?topic=45.0 Pin out with a nice graph
http://pibot.org/forum/index.php?topic=50.0 Raspi A+ is better than V2 in terms of power consumption. See also this post & this new one from raspi.tv.
Turn on wifi (pc/tablet/phone) and connect to TiddlyBot_01 SSID with the password 'Raspberry'. Use the address http://192.168.42.1. When we turn on RasPi, we shall see the wifi led keep flashing. If not, eject uSD and insert again (and boot). If we connect RasPi to a monitor, it will drop to the shell. The default username/password is pi/raspberry (lower case).

The battery it includes is Nokia BL-5C 1020mAh 3.7V 3.8Wh ~ $5.35 US. Note that the battery has 3 pins. One of them labelled as T is for temperature.

To turn off the robot, switch the slider to the buzzer.

To run a small dhcp server, it uses udhcpd.

pi@raspberrypi ~ $ sudo service --status-all
 [ ? ]  alsa-utils
 [ - ]  bootlogs
 [ ? ]  bootmisc.sh
 [ ? ]  cgroup-bin
 [ ? ]  checkfs.sh
 [ ? ]  checkroot-bootclean.sh
 [ - ]  checkroot.sh
 [ - ]  console-setup
 [ + ]  cron
 [ + ]  dbus
 [ ? ]  dphys-swapfile
 [ ? ]  fake-hwclock
 [ + ]  hostapd
 [ - ]  hostname.sh
 [ ? ]  hwclock.sh
 [ + ]  ifplugd
 [ - ]  kbd
 [ - ]  keyboard-setup
 [ ? ]  killprocs
 [ ? ]  kmod
 [ - ]  lightdm
 [ - ]  motd
 [ ? ]  mountall-bootclean.sh
 [ ? ]  mountall.sh
 [ ? ]  mountdevsubfs.sh
 [ ? ]  mountkernfs.sh
 [ ? ]  mountnfs-bootclean.sh
 [ ? ]  mountnfs.sh
 [ ? ]  mtab.sh
 [ ? ]  networking
 [ - ]  nfs-common
 [ + ]  ntp
 [ ? ]  plymouth
 [ ? ]  plymouth-log
 [ - ]  procps
 [ ? ]  raspi-config
 [ ? ]  rc.local
 [ - ]  rmnologin
 [ - ]  rpcbind
 [ - ]  rsync
 [ + ]  rsyslog
 [ ? ]  screen-cleanup
 [ ? ]  sendsigs
 [ + ]  ssh
 [ - ]  sudo
 [ + ]  triggerhappy
 [ + ]  udev
 [ ? ]  udev-mtab
 [ ? ]  udhcpd
 [ ? ]  umountfs
 [ ? ]  umountnfs.sh
 [ ? ]  umountroot
 [ - ]  urandom
 [ - ]  x11-common

Live stream to youtube

Live Stream to YouTube With a Raspberry Pi from makeuseof.
Live stream to YouTube with your Raspberry Pi and Docker

Bird feed

Raspberry Pi catches the early bird

View Stonehenge in real time via Raspberry Pi

View Stonehenge in real time via Raspberry Pi and the site.

ESP8266

Connect an ESP8266 to your RaspberryPi

IFTTT

See Fridge monitor (p41-45) of TheMagPi September 2015.

Control a 12V lamp with GPIO ZERO

http://raspi.tv/2015/gpio-zero-test-drive-making-light-of-security

Grandpa scarer & Laser cutter

https://www.raspberrypi.org/learning/grandpa-scarer/worksheet/

Color sensing

https://www.raspberrypi.org/blog/colour-sensing-raspberry-pi/

Relay

How to Build a Light-Sensing Smart Switch With Raspberry Pi and IFTTT

Smart suitcase

http://www.instructables.com/id/How-to-Make-a-Smart-Suitcase-With-a-Raspberry-Pi/

Other cool stuff

Home Automation

OpenHAB
Linux User & Developer Part 1, Part 2

Uses in office

11 Uses for a Raspberry Pi Around the Office. DNS Server, Toilet Occupied Sign, Honeypot Trap for Hackers, Print Server, Network Attached Storage, Ticketing Server, Digital Signage, Directories and Kiosks, Basic Intranet Web Server, Penetration Tester, VPN Server, and Wireless Coffee Machine.

Track Internet Dropouts

http://makezine.com/projects/send-ticket-isp-when-your-internet-drops/. Keywords: speedtest-cli, cron, IFTTT, google spreadsheet.
PCWorld

GPS tracker

http://blog.initialstate.com/new-python-gps-tracker/

Retro Game Console/Emulator

Super NES Classic loaded with 21 games! The Best Retro And Mini Console Gifts Dec 2018
Online emulator (require adobe flash; eg Google Chrome)
5 ways to play old-school games on a Raspberry Pi
RetroPie
- How to Install RetroPie as an App in Raspbian on Raspberry Pi
- How to transfer ROM from your primary computer
Super Ninetendo Pi
Running OpenGL-based Games & Emulators on Adafruit PiTFT Displays
Linux Gaming: Nintendo 64 Emulation on Odroid.
ROMS
SNES EZ Key Bluefruit Game Pad
http://makezine.com/projects/build-retro-gaming-console-raspberry-pi/
http://lifehacker.com/how-to-turn-your-raspberry-pi-into-a-retro-game-console-498561192
Pixel Vision - a console capable of emulating some of the most classic game systems.

Username: pi, password: raspberry. See RetroPie wiki.

$ ssh [email protected]
[email protected]'s password:

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Wed May 11 17:35:37 2016 from 10.42.0.1

   .~~.   .~~.    Wednesday, 11 May 2016,  5:36:53 pm UTC
  '. \ ' ' / .'   Linux 4.1.19+ armv6l GNU/Linux
   .~ .~~~..~.
  : .~.'~'.~. :   Filesystem      Size  Used Avail Use% Mounted on
 ~ (   ) (   ) ~  /dev/root        15G  2.2G   12G  16% /
( : '~'.~.'~' : ) Uptime.............: 0 days, 00h04m04s
 ~ .~       ~. ~  Memory.............: 114884kB (Free) / 250692kB (Total)
  (   |   |   )   Running Processes..: 70
  '~         ~'   IP Address.........: 10.42.0.37
    *--~-~--*     Temperature........: CPU: 46°C/114°F GPU: 46°C/114°F
                  The RetroPie Project, http://www.petrockblock.com

pi@retropie:~ $ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/root        15G  2.2G   12G  16% /
devtmpfs        119M     0  119M   0% /dev
tmpfs           123M     0  123M   0% /dev/shm
tmpfs           123M  8.5M  114M   7% /run
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           123M     0  123M   0% /sys/fs/cgroup
/dev/mmcblk0p1   57M   20M   38M  35% /boot

pygame

Three great games from GameMaker: Studio

https://www.raspberrypi.org/blog/three-great-gamemaker-games-raspberry-pi/

Raspberry Pi Based Wireless FM Microphone

http://www.instructables.com/id/Raspberry-Pi-Based-Wireless-Microphone/?ALLSTEPS

Dashboard/Kiosk by dashing.io

See the article USE AN ODROID-C1 AS A WALL DASHBOARD on 2015/5 ODROID magazine
http://www.fusonic.net/en/blog/2013/07/31/diy-info-screen-using-raspberry-pi-dashing/
Search google: dashing raspberry pi

Ashley’s top five projects for Raspberry Pi first-timers

https://www.raspberrypi.org/blog/ashleys-top-five-projects-for-raspberry-pi-first-timers/

5 Raspberry Pi Digital Signage Projects You Should Try

https://www.makeuseof.com/tag/raspberry-pi-digital-signage-projects/

6 Raspberry Pi tutorials to try out

https://opensource.com/article/20/3/raspberry-pi-tutorials

VPN server
Create an object-tracking camera
Photo slideshow
Retro game
Build a clock for your entertainment center

Go to space

Raspberry Pi in space (nearly) 35.5 km Pi balloon launch and a GoPro version.

OpenCV

Face recognition treasure box from adafruit.

Wii Remote, bluetooth

Wii remote based on CWiid Python library (it works on my UDOObuntu 2). Another very similar example.
Controlling an i-racer RC car using a Wii Balance Board and Raspberry_Pi
Wii Nunchuck and C code. This is based on Python.
WiiChuck Adapter
CamJam Edukit 3 Robotics Kit no instruction.

Wii balance board

https://en.wikipedia.org/wiki/Wii_Balance_Board
Smart beer fridge with wii balance board and Raspberry Pi (ARM). The weight scale example works fine when I tested on UDOO. Plus there are only 3 packages to install (python-bluetooth, bluez and python-gobject).
Wii-Scale and Web page
DIY internet-enabled bathroom scale
A Hackable, Weight Tracking, Text Messaging Scale with a Sense of Humor
Use the Wii Balance Board as a pretty accurate weight scale How to use?
Sends weight to Google Docs spreadsheet, shows it on an LCD and outputs text to speech
https://www.hackster.io/claude4/wii-balance-board-cloud-scale-400a4b
Wii balance board with GUI (tested on UDOObuntu 2 beta2 based on Ubuntu 14.04.3 LTS, Nov 2015 AND Raspbian on Raspberry Pi Dec 2017). One inconvenient thing is I need to press the sync button every time I run the program.

sudo apt-get install autoconf autogen automake gcc bluetooth libbluetooth3-dev \
          libgtk2.0-dev pkg-config python2.7-dev flex bison git-core \
          libbluetooth-dev python-pygame python-tk
          # NOTE: libbluetooth2-dev becomes libbluetooth3-dev now
          #       python2.5-dev becomes python2.7-dev now
sudo apt-get install bluez
                                                   # no need to create wiibalance directory
git clone https://github.com/abstrakraft/cwiid.git # the svn method does not work
                                                   # 131 commits. Last commit is Feb 21, 2010.
cd cwiid
aclocal
autoconf  # if something messed up, run 'autoreconf'

# Follow http://wiki.labomedia.org/index.php/Blender:Wiimote_:_Compilation_de_cwiid_sur_Linux_Mint_12
#   to fix an error "wmdemo undefined reference to symbol str2ba" when running 'make'
#   That is, edit wmdemo/Makefile.in line 11
#   LDLIBS += -lcwiid -lbluetooth
# make clean
sed -i 's/lcwiid/lcwiid -lbluetooth/g' wmdemo/Makefile.in
./configure        # no need of '--libdir=/usr/lib'
make
sudo make install

# Test Wii remote with GUI
sudo wmgui/wmgui

cd python
sudo python setup.py install
#  install the Wii balance board software:
git clone git://github.com/videntity/python-omhe.git
cd python-omhe
sudo python setup.py install

# Install pycurl; see https://www.raspberrypi.org/forums/viewtopic.php?f=32&t=103188
sudo apt-get install python-pycurl
sudo python ./omhe/hardware/wiibalance/wiibal-weighdemo.py     
# Strangely, the code is for bal board but the instruction is for Wiimote
# Just ignore this test and/or its result

wget http://abstrakraft.org/cwiid/raw-attachment/ticket/63/scalesgui.py
wget http://abstrakraft.org/cwiid/raw-attachment/ticket/63/system.ini
chmod a+x scalesgui.py
nano system.ini # On my 800x480 display, I change <system.ini> file
                # width=1200 -> 800, height=960 -> 420, size=300 -> 50
                # On Pi-top (1366 x 768), I use width = 1200, height = 650
nano scalesgui.py # change line 170 in order to change kg to pounds
                  # weight_sprite.weight = weight*2.20462
                  # change line 161 to use 'q' letter instead of 'F1' to quit the program
                  # if event.key == K_q:
sudo python ./scalesgui.py  # better to keep pressing the red sync button until ...
                            # <system.ini> and <scalesgui.py> are in the same dir
#  To exit the program you should press the “F12” key.
#  I change the code in scalesguy.py to use the 'q' key to quit the program.

Robot control

Compile R from source

Tested on R 3.0.1

cd R-3.0.1
./configure --with-recommended-packages=no
sudo apt-get install openjdk-7-jdk
nano src/library/tools/R/install.R and pass "perl = TRUE" to sub()

SHLIB_EXT <- sub(".*= ", "", grep("^SHLIB_EXT", mconf, value = TRUE), perl = TRUE)
SHLIB_LIBADD <- sub(".*= ", "", grep("^SHLIB_LIBADD", mconf, value = TRUE), perl = TRUE)

to get rid of the error gcc: error: SHLIB_LIBADD: No such file or directory.

make

Temperature/Humidity Sensors for Data Analysis in R

Setting Up Raspberry Pi Temperature/Humidity Sensors for Data Analysis in R

Google Coder

PS. Code is based on node.js (Early version of shiny-server also depends on node.js).

http://pi.gadgetoid.com teaches us how to install Coder on a Raspberry Pi running on Raspbian. Note that Coder can turn Raspberry Pi into a web server. We can develop the code on a remote computer.

In fact, it is possible to run Code for Raspberry Pi on your own PC. Just run 7 lines of script at here. Note: My experience shows it is safe to use the version on Sep-17-2013; otherwise you'll get the following error when using 'nodejs server.js'

$ nodejs server.js
no certificate found. generating self signed cert.

module.js:337
    throw new Error("Cannot find module '" + request + "'");
          ^
Error: Cannot find module '/home/pi/coder/coder-base/apps/auth/app'

So the successful steps to install coder on Ubuntu is

download zip file from Sep-17-2013 tree
cd coder-base; npm install
modify 'config.js'
launch it by 'node server.js'.

I don't have to use sudo when I use 'npm install' and 'node server.js'.

The password requirement for coder is at least 6 characters, at least one lower case and at least 2 upper cases or numbers.

Also, on Ubuntu it will complain the user 'pi' does not exist. So we shall do this 'sudo adduser pi' too. Pick the same password as we use in coder (eg Raspberry99).

Update: After I played with it, I found Coder does not let us work on more than one HTML, CSS or Javscript file. This makes the development more difficult.

Another choice is to run Cloud9 IDE on RPi. The Cloud 9 IDE was preinstalled on Beaglebone black/

Wolframe Mathematica

http://www.wolfram.com/raspberry-pi/
http://www.wolfram.com/broadcast/video.php?channel=105/?fp=left&video=1571 (Video)
http://www.raspberrypi.org/archives/5282
http://www.raspberrypi.org/phpBB3/viewtopic.php?t=61746&p=459159 (Download locally first)

For some reason, the Mathematica is not shown on the menu (it only happened on self-installed version). We can start Mathematica from the command line

/usr/bin/mathematica

We can try a 3D plot like seen in youtube

Plot3D[Sin[x*y], {x,0,Pi}, {y,0,Pi}]

The following screenshot shows how to calculate the derivative of f(x)=sin(x)*exp(2x) using Wolfram.

Note that the language is case-sensitive. For example, sin[x] is not recognized and it should be Sin[x].
Wolfram language uses square brackets instead of parentheses for function's arguments.
See this page for Wolfram language & system documentation.
Another way is to type D[Sin[x] * Exp[2x], x]

Note that Mathematica is a GUI program so it is kind of slow when it is running on Raspberry Pi. The Wolfram program is a command line interface program so it is much faster although we can not do any plotting there.

Use RaspPi as Media Center

http://www.packtpub.com/raspberry-pi-media-center/book

IN-FLIGHT entertainment system

https://youtu.be/QESAI93Uqyg

Record TV

http://www.redrobe.com/mike/record-tv-on-raspberry-pi-with-tvheadend/. This is from the same author of Raspicam Remote for Android.

Bitcoin Miner

Wifi extender

RaspAP Web interface to control wifi, hostapd and related services
Hostapd : The Linux Way to create Virtual Wifi Access Point
Simple Raspberry Pi WiFi Extender
How to Setup a Wireless Access Point on the Raspberry Pi

# 1. Update
sudo apt update; sudo apt upgrade

# 2. Install software
sudo apt install dnsmasq hostapd

# 3. Setup wlan0 (if this has been done before, go to step 5)
sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

# 4. Create an entry of 
network={
  ssid=" "  
  psk=" " 
}

# 5. Setup dhcpcd
sudo nano /etc/dhcpcd.conf

# 6. Add lines 
interface wlan1
static ip_address=192.168.220.1/24
static routers=192.168.220.0

# 7. Restart dhcpd service
sudo service dhcpcd restart

# 8. Adjust hostapd configuration
sudo nano /etc/hostapd/hostapd.conf

# 9. Adjust the ssid=, wpa_passphrase= and 
#    driver= line to the best driver for your device,
interface=wlan1
driver=nl80211

hw_mode=g
channel=6
ieee80211n=1
wmm_enabled=1
ht_capab=[HT40][SHORT-GI-20][DSSS_CCK-40]
macaddr_acl=0
ignore_broadcast_ssid=0

auth_algs=1
wpa=2
wpa_key_mgmt=WPA-PSK
rsn_pairwise=CCMP

ssid=Pi3-Extender
wpa_passphrase=raspberry

# 10. 
sudo nano /etc/default/hostapd

# 11. 
Replace the line
#DAEMON_CONF=""
with 
DAEMON_CONF="/etc/hostapd/hostapd.conf"

# 12. 
sudo nano /etc/init.d/hostapd

# 13.
Replace the line 
#DAEMON_CONF=
with 
DAEMON_CONF=/etc/hostapd/hostapd.conf

# 14. setting up dnsmasq
sudo mv /etc/dnsmasq.conf /etc/dnsmasq.conf.orig

# 15. 
sudo nano /etc/dnsmasq.conf

# 16. add the following lines
interface=wlan1       # Use interface wlan1  
listen-address=192.168.220.1   # Specify the address to listen on  
bind-interfaces      # Bind to the interface
server=8.8.8.8       # Use Google DNS  
domain-needed        # Don't forward short names  
bogus-priv           # Drop the non-routed address spaces.  
dhcp-range=192.168.220.50,192.168.220.150,12h # IP range and lease time

# 17. forward all traffic from our wlan1 connection over to our wlan0 connection
sudo nano /etc/sysctl.conf

# 18. 
Replace the line
#net.ipv4.ip_forward=1
with
net.ipv4.ip_forward=1

# 19. 
sudo sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"

# 20. configure a NAT between our wlan0 interface and our wlan1 interface. 
sudo iptables -t nat -A POSTROUTING -o wlan0 -j MASQUERADE  
sudo iptables -A FORWARD -i wlan0 -o wlan1 -m state --state RELATED,ESTABLISHED -j ACCEPT  
sudo iptables -A FORWARD -i wlan1 -o wlan0 -j ACCEPT

# 21.
sudo sh -c "iptables-save > /etc/iptables.ipv4.nat"

# 22.
sudo nano /etc/rc.local

# 23.
Find the line
exit 0
Add ABOVE:
iptables-restore < /etc/iptables.ipv4.nat

# 24.  start the two services and enable them in systemctl.
sudo systemctl unmask hostapd
sudo systemctl enable hostapd
sudo service hostapd start
sudo service dnsmasq start

# 25. sudo nano /etc/network/interfaces 
allow-hotplug wlan0
iface wlan0 inet dhcp
# wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
allow-hotplug wlan1

# 26. sudo reboot

I can see the SSID. But I cannot connect to that.

sudo systemctl status hostapd
sudo systemctl status dnsmasq

Turn Raspi into a wireless hotspot / access point

I am using TP-LINK TP-WN722N wifi adapter.

(Not stable) http://elinux.org/RPI-Wireless-Hotspot. Also see some of my notes on Beaglebone page. The instruction asks to install hostapd and udhcpd (not dhcp). I made a copy of the changed files in Github. It appears there is a typo on the /etc/udhcpd.conf file. See Setting up Pi as a Wifi Hotspot. That is, use option instead of opt on subnet and lease lines. Issue 1: I have a problem with automatically or manually starting udhcpd service. Issue 2: even the hotspot is connected but no internet was found. See
- http://askubuntu.com/questions/699995/hotspot-created-and-connected-from-linux-but-no-internet-access-on-phone
- http://superuser.com/questions/1061849/connected-to-hostapd-hotspot-but-no-internet
- I found out a solution for my case. Running 'ifconfig' and 'route -n', my problem is the wlan0 ip is wrong (becomes 169.254.0.0). So I need to run sudo ifdown wlan0 && sudo ifup wlan0 or better sudo /etc/init.d/networking restart to fix the ip error.
```
pi@raspberrypi:~ $ route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         10.42.0.1       0.0.0.0         UG    202    0        0 eth0
10.42.0.0       0.0.0.0         255.255.255.0   U     202    0        0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U     303    0        0 wlan0
192.168.42.0    0.0.0.0         255.255.255.0   U     0      0        0 wlan0
pi@raspberrypi:~ $ ifconfig
eth0      Link encap:Ethernet  HWaddr b8:27:eb:24:6b:a0  
          inet addr:10.42.0.37  Bcast:10.42.0.255  Mask:255.255.255.0
          ...

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          ...

wlan0     Link encap:Ethernet  HWaddr f8:d1:11:0b:52:6f  
          inet addr:192.168.42.1  Bcast:192.168.42.255  Mask:255.255.255.0
          ...
```
(Adafruit) Setting up a Raspberry Pi as a WiFi access point by installing hostapd and isc-dhcp-server packages. The instruction works and looks quite stable after I reboot Pi a few times. I found I don't need to run the final two lines to start the daemon services.
```
sudo service hostapd status
sudo service isc-dhcp-server status
```
(Adafruit) You can setup wlan0 in standalone mode or bridge it with eth0. Digital Free Library also includes how to set up Raspi as an access point/apache server/dhcp server (but no internet connection).
http://raspberry-at-home.com/hotspot-wifi-access-point/
Turn Your Raspberry Pi Into a WiFi Hotspot with Edimax Nano USB EW-7811Un. This instruction is using bridge-utils and hostapd packages.
Setup Wireless Access Point (WAP) with Hostapd for Debian/Ubuntu by installing hostapd & bridge-utils packages.
This is a similar post using hostapd and isc-dhcp-server packages.

How to Turn Your Raspberry Pi into a Wireless Access Point (2020)

1. Install hostapd, dnsmasq, FW plugins
2. Assign a static IP	/etc/dhcpcd.conf
3. Enable routing	/etc/sysctl.d/routed-ap.conf
4. Configure DHCP and DNS	/etc/dnsmasq.conf
5. Create a network name and pw	/etc/hostapd/hostapd.conf

Midi keyboard

SamplerBox - Akai LPK25 keyboard.

Bike computer

https://www.raspberrypi.org/blog/bike-computer-for-the-myopic/ This build uses the Kindle as a display

OctoPrint

The snappy web interface for your 3D printer.

Connect your printer to a small embedded and WiFi enabled device such as the popular Raspberry Pi, install OctoPrint on it and you have an instant wireless printer.

Orange Pi

Mozilla Project Things

https://iot.mozilla.org/

E-ink

https://twitter.com/hashtag/epaper
Using E Ink displays with a Raspberry Pi
Weather Station with ePaper and Raspberry Pi 2020
Waveshare hardware connection from Github (4 SPI pins are needed). The first number (eg RES white -> 11) below is from a continuous sequence order (physical location) and the 2nd number (eg BCM: 17) is GPIO number (or BCM pin number).

    EPD         =>  Raspberry Pi
  * VCC  red    ->  3.3
  * GND  black  ->  GND
  * DIN  blue   ->  19 MOSI
  * CLK  yellow ->  23 SCLK
  * CS   orange ->  24 (Physical, BCM: CE0, 8)
  * D/C  green  ->  22 (Physical, BCM: 25)
  * RES  white  ->  11 (Physical, BCM: 17)
  * BUSY purple ->  18 (Physical, BCM: 24)

vcc	red	1	3v3
gnd	black	6	ground
rst	white	11	gpio17
busy	purple	18	gpio24
din	blue	19	gpio10 (spi mosi)
dc	green	22	gpio025
clk	yellow	23	gpio11 (spi sck)
cs	orange	24	gpio08 (spi ce0)

Test Waveshare ePaper (eInk) 2.7” inch 264×176 SPI screen on Raspberry Pi in Python. Refresh time 6s.
- https://www.waveshare.com/wiki/2.7inch_e-Paper_HAT and github example. Five steps were needed to show a screen. 1. Reverse 2. White 3. Black 4. Reverse 5. Normal.
- Clock and weather display for E-Paper 2.7 inch display from Waveshare for Raspberry Pi 3. The screen will refresh every minute (use CPU). It does work but the temperature is in C not F. To fix that, open "epaper.py" file, change the variable "DARK_SKY_UNITS" from "si" to "auto"; see Doc from darksky.net. The cpu and memory usage shown on the screen is different from what I saw from the result of 'htop' (over estimate). Note that darksky.net web information is incredible friendly already. Apple acquires Dark Sky weather app (3/30/2020).

sudo apt-get install libjpeg-dev
pip install -r requirements.txt
chmod +x run.sh
./run.sh  # DO NOT ADD sudo
# terminal will show messages from the code. For example, press button 4
# [Button] Btn #4 pressed
# [Button] Btn press handled.
# App is shuting down.
# Display shutdown icon ...
# [Epaper] Display.
# ... done.
# calling exit 0

- Once we put the program in a service, it is tricky to change the settings. It is best to stop the service before doing any change; sudo systemctl stop epaper.service . Then we need to delete all auto-generated *.pyc file; find . -iname "*.pyc" -delete. Now we can start the service again; sudo systemctl start epaper.service .
- If the program was run through the service, press button 4 will shut down the code but the script will be launched again.
- Understand the code. Search shutting_down, shutdown_hook, pressed keywords
Waveshare ePaper 4.2 inch 400 × 300. Refresh time 4s.
- https://github.com/waveshare/e-Paper/tree/master/2.7inch_e-paper_code/RaspberryPi/python3 shows what software we need to install.
```
sudo apt-get install python-pip 
sudo pip install RPi.GPIO
sudo pip install spidev
sudo apt-get install ttf-wqy-zenhei ttf-wqy-microhei
```
- http://www.waveshare.net/wiki/4.2inch_e-Paper_Module. Click on 示例程序 to download 4.2inch_e-paper_code.7z.
```
wget http://www.waveshare.net/w/upload/8/80/4.2inch_e-paper_code.7z
mkdir 4.2inch_e-paper_code
cd 4.2inch_e-paper_code
sudo apt-get install p7zip-full
# It seems the "e" option from 7za will not keep the directory structure properly
# We need to use the "x" option.
7za x ../4.2inch_e-paper_code.7z # https://superuser.com/a/379594
cd RaspberryPi/python3
```
  Then follow the 用户手册/manual (useful) to install required software and run the demo. Note when installing the Pillow library (sudo pip3 install Pillow), I got an error: The headers or library files could not be found for jpeg. To fix the problem, try
```
# The original instruction in the manual does not help
# sudo apt install libopenjp2-7-dev 
sudo apt-get install libjpeg-dev
```
  Don't forget to enable SPI (sudo raspi-config) before running "sudo python main.py". I actually got another error complaining font24 = ImageFont.truetype('/usr/share/fonts/truetype/wqy/wqy-microhei.ttc', 24). Follow the suggestion 2.13 epaper display problem and install the required font by sudo apt-get install fonts-wqy-microhei, I am able to run the demo program.

In order to resize an image to 400x300 and monotone scale (see the last page of the manual), we can use

sudo apt-get install imagemagick
wget http://worldartsme.com/images/spring-charlie-brown-clipart-1.jpg -O spring.jpg
convert spring.jpg -format bmp -resize 400x300! -monochrome 4in2_spring.bmp
cp 4in2.bmp 4in2_original.bmp
cp 4in2_spring.bmp 4in2.bmp
sudo python3 main.py
# notice the exclamation mark, "!". 
# See http://www.imagemagick.org/script/command-line-processing.php#geometry

E-ink calendar using a Raspberry Pi Zero
Raspberry Pi: an E-Paper display with Widgets Waveshare® 7.5" E-ink Screen.
Comparison of different e-inks from Waveshare.net. Note the 7.5 inch epaper has a resolution 640x384 (cf 7 inch 800x400 official raspberry pi display).
Aliexpress
You can build a DIY E Ink “magic mirror” for under $100
- Waveshare e-Paper python demo code to install on the Raspberry Pi 3 - raspbian eink
PaPiRus: ePaper Screen HAT for your Raspberry Pi

Magic mirror

How to measure particulate matter

https://opensource.com/article/18/3/how-measure-particulate-matter-raspberry-pi. Lighttpd, HTML, JavaScript, and CSS are used.
How to build a mobile particulate matter sensor with a Raspberry Pi

Alternatives

BeagleBone Black (no built-in wifi or bluetooth)
UDOO with built-in wifi. Bluetooth relies on USB.
ODROID H2 Celeron J4105, M.2 PCIe 2.0 x4 slot for one NVMe storage, 2x SATA 3.0 ports, eMMC flash support
Atomic Pi x386. Atom x5-Z8350 benchmark: 1268.
Rock Pi 4B: RK3399 cpu, M.2 NVME SSD & USB 3.0
RockPro64 from pine64.org
Orange Pi 3. Not good. See the review by explainingcomputers.com.
NanoPi NEO4 supports PCIe. Rockchip RK3399.

@@ Line 630: / Line 630: @@
 * [https://www.stewright.me/2017/06/install-raspbian-usb-flash-drive-macos-linux/ Install Raspbian on a USB Flash drive from MacOS or Linux]
 * [https://thepi.io/how-to-boot-your-raspberry-pi-from-a-usb-mass-storage-device/ How to boot your Raspberry Pi from a USB mass storage device]
+* [https://www.pcmarket.com.hk/2020/05/22/告別microsd-usb裝置起動-raspberry-pi-4測試版靭體推出/ 告別 microSD USB 裝置起動　Raspberry Pi 4 測試版靭體推出]
 == Put /root in USB ==

Raspberry: Difference between revisions

Revision as of 09:18, 25 May 2020