Raspberry: Difference between revisions

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== Grandpa scarer & Laser cutter ==
== Grandpa scarer & Laser cutter ==
https://www.raspberrypi.org/learning/grandpa-scarer/worksheet/
https://www.raspberrypi.org/learning/grandpa-scarer/worksheet/
== Color sensing ==
https://www.raspberrypi.org/blog/colour-sensing-raspberry-pi/


= Other cool stuff =
= Other cool stuff =

Revision as of 12:33, 18 April 2018

Raspberry Pi

Miscellaneous

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

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

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

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

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.

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). 

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

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.

Set up a static IP address

sudo systemctl stop dhcpcd.service  # deactivate dhcpcd
sudo nano /etc/network/interfaces

The original interfaces file looks like 

# interfaces(5) file used by ifup(8) and ifdown(8)

# Please note that this file is written to be used with dhcpcd
# For static IP, consult /etc/dhcpcd.conf and 'man dhcpcd.conf'

# Include files from /etc/network/interfaces.d:
source-directory /etc/network/interfaces.d

auto lo
iface lo inet loopback

iface eth0 inet manual

allow-hotplug wlan0
iface wlan0 inet manual
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

allow-hotplug wlan1
iface wlan1 inet manual
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

The new interfaces file will look like (You can set either or both eth0 or wlan0). Don't forget to include auto eth0 or it won't work!! auto is used to bring up the interface when ifup is run with the -a option. (This option is used by the system boot scripts.) 

auto eth0
iface eth0 inet static
        address 192.168.1.88
        netmask 255.255.255.0
        gateway 192.168.1.1
        dns-nameservers 8.8.8.8 8.8.4.4

allow-hotplug wlan0
iface wlan0 inet static
        address 192.168.1.89
        netmask 255.255.255.0
        gateway 192.168.1.1
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

Then disable the DHCP client daemon and switch to standard Debian networking: 

sudo systemctl disable dhcpcd
sudo systemctl enable networking
sudo reboot # Reboot for the changes to take effect:

The DNS server part can be placed on /etc/resolv.conf file 

search domain.com
nameserver xxx.xxx.xxx.xxx

Note that the search keyword works when users are not typing FQDN then the search domains will be tried.

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 monitor

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.

The official Raspberry Pi DSI touch display

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. 

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).

Startup script

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

CPU Benchmark

# 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

Picademy

UPS

Books, Magazines

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.

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.

  • 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)

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.

Boot from USB

Pi Desktop

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

Remote desktop

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

RealVNC server

  • Do not download the binary from RealVNC website since it will have a license issue when we want to connect to RPi
  • Use the instruction at Github
  • On linux client side, we can download the binary tar ball and set it executable after untar it.

Connect to Your Raspberry Pi From Anywhere In World With VNC Connect

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/

Raspbian repository and mirrors

Releases lists

Raspbian package repository URL

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

Fix Dirty COW

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

Kernel building

Create a custom kernel using Vagrant

Emulate Raspbian on Linux/Windows

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.

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.

Turn Raspberry Pi Zero into a USB gadget

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

  1. http://openelec.tv/get-openelec
  2. http://wiki.openelec.tv/index.php/HOW-TO:Installing_OpenELEC/Writing_The_Disk_Image

SMS server

Kodi black screen when exit

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

    #!/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

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 server

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

DNS server

Pi hole

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.

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

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

Done!

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

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.

Mate1510Raspbery.png Mate1510Raspbery2.png

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.

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

  1. System -> Adminstration -> Printers -> Add
  2. 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)
  3. Check the 2nd option 'Provide PPD file' instead of the 1st one 'Select printer from database'.
  4. Browse the location of the PPD file
  5. 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!!!

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.

pi-top

I pledged pi-topCEED ($99 + shipping is $25). The hardware looks cool: 14 inch, 1366x768 resolution & 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).

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.

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

  • 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)
  • Cable 3: connect to pins 26

Pitop1.jpg Pitophub.jpg Raspi3.jpg

Plex

How to Turn a Raspberry Pi into a Cheap Plex Player with RasPlex

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/

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.

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

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. Basic knowledge on internet protocol. However, it is slow and show all instead of found ip's.
  • netbios. It does not discover linux boxes, however.

Clustering

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

Docker swarm

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

Raspberry Pi 2

Raspberry Pi 2 (Armv7 with quad core cpu and 1GB RAM) brings its hardware to the minimum requirements for several interesting projects. I got one from my local microcenter store ($35 + tax).

One interesting thing is the Raspbian or Docker supports Raspberry Pi 1 and 2 (different ARM architectures).

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

SnappyRaspPi.png

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

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

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

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.

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.

Ftdi2ttlRaspPi.png

C libraries

GPIO layout

The following picture was taken from www.raspberrypi-spy.co.uk

Raspberry-Pi-GPIO-Layout-Revision-2.png

The following cheatsheet was taken from http://raspi.tv/wp-content/uploads/2013/04/raspberry-pi-gpio-cheat-sheet.jpg

Raspberry-pi-gpio-cheat-sheet.jpg

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 interface to control wifi, hostapd and related services

RaspAP

Web.py

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

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

<youtube>xWJZRK4W13Q</youtube>

  • 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.

SingleLED.jpg 

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()
  • 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.

RpyLCD.jpg

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

MatrixLED.jpg

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

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

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 Raspberry Pi by Lipo batteries

Solar power

Add a push button

Speech synthesis and a push button

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

http://learn.adafruit.com/adafruits-raspberry-pi-lesson-8-using-a-servo-motor?view=all

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.

MCP23017 GPIO expander (extra 16 pins)

Serial Peripheral interface (SPI)

http://www.brianhensley.net/2012/07/getting-spi-working-on-raspberry-pi.html

Camera

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 myvid.mp4

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).

Dash Cam

Create a button-operated camera

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

RPi Cam (Live stream and Cam Web Interface) by Bob Tidey

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

RPi Cam Web.png RPi Cam Web2.png

Security Camera

Intruder detection

http://www.instructables.com/id/Intruder-Detector-With-Raspberry-Pi-and-Pushbullet/

Pan and tilt security camera controlled by Arduino

http://www.makeuseof.com/tag/diy-pan-and-tilt-network-security-cam-raspberry-pi/

Slow motion

http://www.averagemanvsraspberrypi.com/2015/07/raspberry-pi-camera-module-slow-motion-video.html

Motion triggered infrared wildlife camera

https://blog.adafruit.com/2015/09/04/how-to-make-a-motion-triggered-infrared-wildlife-camera-with-raspberry-pi-piday-raspberrypi-raspberry_pi/

How Do Night Vision Cameras Work?

Solar powered nature camera

https://www.raspberrypi.org/blog/solar-powered-nature-camera/

Baby monitor

Tiddlybot

Tiddlybot.jpg

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

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/

Other cool stuff

Home Automation

Track Internet Dropouts

GPS tracker

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

Retro Game Console/Emulator

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

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

Go to space

OpenCV

Wii Remote, bluetooth

Wii balance board

WiiBalBoard.jpg 

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

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

  1. download zip file from Sep-17-2013 tree
  2. cd coder-base; npm install
  3. modify 'config.js'
  4. 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

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]

WolframPi.png

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

Record TV

Bitcoin Miner

Turn Raspi into a wireless hotspot / access point

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

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

Midi 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/

Alternatives

  • BeagleBone Black (no built-in wifi or bluetooth)
  • UDOO with built-in wifi. Bluetooth relies on USB.
  • ODROID (no built-in wifi or bluetooth)
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