Beaglebone

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Official website

Basic

BeagleboneCup.jpg

elinux

Blog, Resource

The meaning of LEDs in BBB board

  1. USR0 is configured at boot to blink in a heartbeat pattern
  2. USR1 is configured at boot to light during microSD card accesses
  3. USR2 is configured at boot to light during CPU activity
  4. USR3 is configured at boot to light during eMMC accesses

BlackUSR.png

Derek Molloy

A series of Youtube videos to introduce Beaglebone. The source code of Video #9 can be downloaded from original website.

  • Video #1 introduction to beaglebone
  • Video #2 C/C++ Programming
  • Video #3 GPIO programming on ARM
  • Video #4 I2C
  • Video #5 USB Wifi & Build Kernel
  • Video #6 Stepper motor
  • Video #7 LCD touchscreen
  • Video #8 Qt Creator
  • Video #9 Example of Qt; shows an application using GPIO + Qt. Video at 1:55 shows how GPIO pins were used for both LCD and LEDs.
  • Video #10 OpenCV
  • Video #11 introduction to GPIO
  • Video #12 Streaming video
  • Video #13 Windows USB network
  • Video #14 JRE, Eclipse

Google Group

https://groups.google.com/forum/#!forum/beagleboard

Debian

Download from http://beagleboard.org/latest-images. Username: debian. Password: temppwd. This distribution contains graphical desktop environment.

  • the source code is hosted in github
  • to rebuild the image, follow the instruction at elinux.org

BbbDebian.png

The Debian version can be found by (version 7 has a codename wheezy) 

debian@beaglebone:~$ cat /etc/debian_version 
7.4

microSD version

It is not necessary but if we want first erase the microSD card, we can issue the following. See this page and wiki page for more dd command examples. 

sudo fdisk -l    # determine the device id
export DISK=/dev/mmcblk0
sudo dd if=/dev/zero of=${DISK} bs=1024 count=1024

It is enough to just run the following 

sudo dd bs=1M if=bone-debian-7.4-2014-03-04-2gb.img of=/dev/sdc
sudo sync

Hold the button close to microSD card and apply power.

The partition table from gparted looks like

MicroSD BBB.png

emmc version

sudo dd bs=1M if=BBB-eMMC-flasher-debian-7.4-2014-03-04-2gb.img of=/dev/sdc
sudo sync

Doing more in LXDE

Root terminal

  • To enable the root account, type sudo passwd root
  • To disable root access, type sudo passwd -l root

Ubuntu/Debian

  • Hold the S2 button & power on BBB. 1st and 3rd LEDs blink.

eMMC version (info was outdated now)

  1. wget the image
  2. Use sudo su instead su to have full root permission. Use xz command to write the image to microSD
  3. Insert microSD to BBB and holding the button (closest to microSD) while applying power on BBB
  4. To copy the image to eMMC, use wget again to get the image file. Use sudo su instead su to have full root permission. Then use xz command again to write the image to eMMC.
  5. Remove microSD and reboot BBB. If we keep microSD in BBB, it will boot from microSD. MicroSD has the advantage that we can extend the space while eMMC cannot.
  • Kernel is 3.8.
  • The image contains a miniminal Ubuntu system. It only takes 276 MB when I use df -h command to check. So it does not come with a full desktop.
  • Defautl username=ubuntu, password=ubuntu
  • http://robotic-controls.com/learn/beaglebone/beaglebone-black-ubuntu
  • If I try to install xubuntu-desktop, it requires 421MB data to download and 1.2GB space to install. So it is not feasible since the /dev/mmcblk0p2 partition has only 1.8GB space. Fortunately, the solution in here works well.
  • Unfortunately, I got an error when I issue 'startx'.
Fatal server error:
AddScreen/ScreenInit failed for driver 0

Please check the log file at "/var/log/Xorg.0.log" for additional informaiton.

After I reboot, things looks better. I can get a login GUI. However, the system is very slow and I can not see mouse on the desktop.

microSD version (with LXDE desktop environment)

PS. Even the emmc version contains LXDE environment. Download from http://beagleboard.org/latest-images

At the beginning, the "/" partition still has 1.4GB space (see table below). If we boot into microSD (using ssh [email protected]) and follow the instruction or this to expand the microSD file system, we can make use whole space in uSD. It involves two commands: one is fdisk (extend the partition) and the other is resize2fs (extend the file system). 

debian@beaglebone:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
rootfs           15G  1.3G   13G  10% /
udev             10M     0   10M   0% /dev
tmpfs           100M  616K   99M   1% /run
/dev/mmcblk0p2   15G  1.3G   13G  10% /
tmpfs           249M     0  249M   0% /dev/shm
tmpfs           249M     0  249M   0% /sys/fs/cgroup
tmpfs           100M     0  100M   0% /run/user
tmpfs           5.0M     0  5.0M   0% /run/lock
/dev/mmcblk0p1   96M   69M   27M  72% /boot/uboot
/dev/mmcblk1p2  1.7G  1.3G  345M  79% /media/rootfs
/dev/mmcblk1p1   96M   72M   25M  75% /media/boot

To find out the Debian version, use 

cat /etc/debian_version

Console version

Following the instruction on robotic-controls.com, we can install the console version of Ubuntu on BBB. The image I download is Ubuntu 13.10 https://rcn-ee.net/deb/rootfs/saucy/ubuntu-13.10-console-armhf-2013-11-15.tar.xz.

This image has some features like 192.168.7.2 access automatically just like Angstrom distribution (I don't know how to get this to work on eMMC version of Ubuntu image). That means I can just connect to BBB without using ethernet under Ubuntu OS.

Installation script (uSD is mounted on /dev/sdc in my case) 

wget https://rcn-ee.net/deb/rootfs/saucy/ubuntu-13.10-console-armhf-2013-11-15.tar.xz
tar xJf ubuntu-13.10-console-armhf-2013-11-15.tar.xz
cd ubuntu-13.10-console-armhf-2013-11-15
sudo ./setup_sdcard.sh --mmc /dev/sdc --uboot bone

The username/password is ubuntu/temppwd.

Below is what I get in HOST os 

brb@brb-P45T-A:~/ubuntu-13.10-console-armhf-2013-11-15$ ifconfig
...
eth2      Link encap:Ethernet  HWaddr 90:59:af:63:df:45  
          inet addr:192.168.7.1  Bcast:192.168.7.3  Mask:255.255.255.252
          inet6 addr: fe80::9259:afff:fe63:df45/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:9 errors:0 dropped:0 overruns:0 frame:0
          TX packets:47 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1010 (1.0 KB)  TX bytes:11690 (11.6 KB)
...

and what I get inside BBB 

ubuntu@arm:~$ ifconfig
eth0      Link encap:Ethernet  HWaddr 90:59:af:63:df:43  
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:56 
...
usb0      Link encap:Ethernet  HWaddr c6:18:a5:e4:60:71  
          inet addr:192.168.7.2  Bcast:192.168.7.3  Mask:255.255.255.252
          inet6 addr: fe80::c418:a5ff:fee4:6071/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:178 errors:0 dropped:0 overruns:0 frame:0
          TX packets:100 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:22583 (22.5 KB)  TX bytes:20013 (20.0 KB)
ubuntu@arm:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/mmcblk0p2   15G  493M   14G   4% /
none            4.0K     0  4.0K   0% /sys/fs/cgroup
udev            247M  4.0K  247M   1% /dev
tmpfs            50M  236K   50M   1% /run
none            5.0M     0  5.0M   0% /run/lock
none            248M     0  248M   0% /run/shm
none            100M     0  100M   0% /run/user
/dev/mmcblk0p1   64M   17M   47M  27% /boot/uboot

We can make the Ubuntu talk to internet by using the instruction given in Angstrom section (run sudo su first).

TTL/Serial cable connection

The screenshot below shows we can use a ttl serial cable to log into beaglebone in command line mode. The beaglebone is powered by a 5v usb. The tricky part is the J4 pin （RXD） in BBB should be connected to the TXD pin in ttl cable. Similarly, the J5 （TDX） pin in BBB should be connected to the RXD pin 8n ttl cable. The 3.3v p8n in ttl cable is not used at all.

This post asks NOT to connect the 5V pin from TTL to BBB. The Serial port pin settings is given on elinux.org as linked from codechiefl.wordpress.com.

Check out the beaglebone black system manual (Section 7.5 Serial Header) about the serial debug ports from https://github.com/CircuitCo/BeagleBone-Black/blob/master/BBB_SRM.pdf. 

   BBB        TTL
  ==========
   J1 GND    GND
   J4 (RXD)  TX
   J5 (TXD)   RX

Ftdi2ttlserialcable.jpg

Find out the IP address if we use internet sharing

If we are using ethernet on BBB, we can find out the IP adress by using the following way.

Download fing deb package from overlooksoft website. Install it by double clicking the file in file manager. Issue the following command to find out the IP of beaglebone black (shared computer). The IP of my 2nd ethernet adapter (eth1) is 10.42.0.1. 

sudo fing -n 10.42.0.1/24

Wifi setup command line

dmesg | grep rtl8192
ifconfig wlan0
sudo apt-get install wireless-tools
iwconfig
sudo nano /etc/network/interface
# Made appropriate change on /etc/network/interface
sudo ifup wlan0 // not needed if we have enable wlan0 at boot. 
                // sudo ifconfig wlan0 up
sudo iwlist wlan0 scanning
ping www.google.com

where the file /etc/network/interface should be like 

auto wlan0
iface wlan0 inet dhcp
    wpa-ssid mynetworkname
    wpa-psk mysecretpassphrase

Angstrom

# Umount the uSD card 
mount # find /dev/sdc1
sudo diskfutil unmount /dev/sdc1
ls *.xz

# Copy img file to microSD card. Took about 15-30 minutes.
# Method 1.
tar -xJf BBB-eMMC-flasher-2013.06.20.img.xz
sudo dd bs=1m if=~/Downloads/BBB-eMMC-flasher-2013.06.20.img of=/dev/sdc
sudo sync
# Method 2.
xz -cd BBB-eMMC-flasher-2013.06.20.img.xz > /dev/sdc

Remove the microSD card and insert it fully into BBB uSD card slot.

To flash the BBB: Hold down the 'user boot' button (closes to uSD card slot) and power on BBB until the 4 LED's light up for a few seconds. It will take 30-45 minutes to flash the image onto the eMMC. Once it's done, the 4 LED's will all stay lit up at the same time. You can then power down your BBB, remove uSD and power up BBB.

The username is root. There is not password. We can access it by ssh [email protected].

If we type ifconfig in Angstrom, we find the connection is through usb0 adapter. 

root@beaglebone:~# ifconfig
eth0      Link encap:Ethernet  HWaddr 90:59:AF:63:DF:43  
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
          Interrupt:56 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:12 errors:0 dropped:0 overruns:0 frame:0
          TX packets:12 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:760 (760.0 B)  TX bytes:760 (760.0 B)

usb0      Link encap:Ethernet  HWaddr 86:27:86:2D:45:5C  
          inet addr:192.168.7.2  Bcast:192.168.7.3  Mask:255.255.255.252
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2765 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5003 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:179578 (175.3 KiB)  TX bytes:7067277 (6.7 MiB)

Web server

http://stackoverflow.com/questions/10818459/where-is-the-web-server-root-directory-on-angstrom-linux-beagleboard-beaglebo

Google coder

http://www.adafruit.com/blog/2013/09/17/run-google-coder-on-your-beaglebone-black/

VNC

opkg update
opkg install x11vnc

x11vnc -bg -o %HOME/.x11vnc.log.%VNCDISPLAY -auth /var/run/gdm/auth-for-gdm*/database -display :0  -forever

To start VNC server at bootup and shutdown, check out

Package download

http://www.gigamegablog.com/2012/01/29/beaglebone-linux-101-configuring-angstrom-linux/ 

opkg update
opkg install XXXX
opkg list | grep "gfortran"

However, at least for BBB case, I cannot find gfortran package so I cannot install R. See discussions below

The angstrom linux package browser is the place we can see if packages for BBB Cortex-A8. According to Wikipedia the Cortex-A8 has armv7a architecture. Cortex-A7 (eg pcDuino3) is a smaller, faster, and more power-efficient successor to the Cortex-A8.

On ubuntu, we can use ldconfig -v command to show the installed libraries and their versions. See here. If we like to manually add libraries to ubuntu/debian, we can check the tip here.

beaglebone.local and Avahi/Bonjour/Zeroconf

Instead of typing an IP address, we can use [email protected] to access BBB running on Angstrom OS. The implementation is done by Avahi Daemon/Bonjour/ZeroConf/Multicast.

We can manually install avahi-daemon in ubuntu-armhf by 

sudo apt-get update
sudo apt-get install avahi-daemon

After that, we should be able to ssh [email protected] instead of using IP. PS: not stable. 

brb@brb-P45T-A:~$ ssh [email protected]
ssh: connect to host ubuntu-armhf.local port 22: Connection refused

The real IP address can be found by ping HOSTNAME.local (Updated: use ps -ef | grep avahi to find out the exact hostname used in .local domain because at least one of my Ubuntu machines does not use its hostname exactly)

For the Angstrom OS with beaglebone, I found the IP number is in 192.168.7.2 (same as in the Getting Start page) by using ping command. 

brb@brb-P45T-A:/etc/init$ ping beaglebone.local
PING beaglebone.local (192.168.7.2) 56(84) bytes of data.
brb@brb-P45T-A:/etc/init$ ifconfig
(skip)
eth2      Link encap:Ethernet  HWaddr 90:59:af:63:df:45  
          inet addr:192.168.7.1  Bcast:192.168.7.3  Mask:255.255.255.252

The same method can be applied to Raspberry Pi or Ubuntu. In fact, avahi-daemon is installed by default. We can use ps -ef | grep avahi to check it.

Internet over Ethernet

The host has IP 10.42.0.1 and it is configured as shared instead of DHCP.

The BBB will have eth0: 10.42.0.50 and usb0: 192.168.7.2.

We can use ssh [email protected] to access it. The BBB will have internet access. 

echo "nameserver 8.8.8.8" > /etc/resolv.conf

Internet over USB

On BBB, run 

sudo su
/sbin/route add default gw 192.168.7.1
echo "nameserver 8.8.8.8" >> /etc/resolv.conf
/sbin/route

It is perfectly fine to have multiple lines of nameserver. (IP Masquerade/Share the internet connection + IP forward)

The above procedure of setting gateway is temporary. We can also permanently change the gateway setting by (https://help.ubuntu.com/12.04/serverguide/network-configuration.html) 

nano /etc/network/interfaces

auto lo
iface lo inet loopback
iface usb0 inet static
    address 192.168.7.2
    netmask 255.255.255.0
    network 192.168.7.0
    gateway 192.168.7.1

On host, run 

sudo iptables -A POSTROUTING -t nat -j MASQUERADE
echo 1 | sudo tee /proc/sys/net/ipv4/ip_forward > /dev/null
sudo iptables -t nat -L

Done. Tested on my home ubuntu host machine running 12.04. We can use the last command to show nat table on host machine; See here.

Angstrom

http://beaglebone.cameon.net/home/internet-over-usb

ArchLinux

This post on Archlinux discusses how to get the usb network adapter that is built into the mini-usb power connector working under Arch.

Ubuntu

How to share internet over USB on BBB? http://askubuntu.com/questions/380810/internet-over-usb-on-beaglebone-black

microHDMI to VGA cable

http://circuitco.com/support/index.php?title=BeagleBone_Black_Accessories

Question: How to create EDIT? My NEC monitor supports only 1024 x 768.

Beagleboneblack HDMI page from circuitco.com.

Remote desktop connection

See Raspberry#Connection_to_Raspberry_Pi_with_tightvnc 

# Server side
sudo apt-get install tightvncserver
tightvncserver     # set up the password
vncserver          # this step may not be necessary
vncserver –kill :1

# Client side
xtightvncviewer 10.42.0.50:1 # or xtightvncviewer 192.168.7.2:1 if we use usb0

To start tightvncserver automatically at start, follow the instruction at here to create a new script file under /etc/init.d/ directory and run update-rc.d on the new script. 

debian@beaglebone:~$ sudo nano /etc/init.d/vncserver
[sudo] password for debian: 
debian@beaglebone:~$ sudo chmod +x /etc/init.d/vncserver 
debian@beaglebone:~$ sudo update-rc.d vncserver defaults
update-rc.d: using dependency based boot sequencing
update-rc.d: warning: default start runlevel arguments (2 3 4 5) do not match vncserver Default-Start values (S)
update-rc.d: warning: default stop runlevel arguments (0 1 6) do not match vncserver Default-Stop values (0 6)
insserv: Script vncserver is broken: incomplete LSB comment.
insserv: missing `Required-Stop:'  entry: please add even if empty.
debian@beaglebone:~$ sudo reboot

Despite the warning, it still works. It make a copy of this vncserver file below. Something we may want to change for different scenario is the USER and GEOMETRY parameters. 

#!/bin/sh -e
### BEGIN INIT INFO
# Provides:          vncserver
# Required-Start:    networking
# Default-Start:     S
# Default-Stop:      0 6
### END INIT INFO

# PATH="$PATH:/usr/X11R6/bin/"

# The Username:Group that will run VNC
export USER="debian"
#${RUNAS}

# The display that VNC will use
DISPLAY="1"

# Color depth (between 8 and 32)
DEPTH="16"

# The Desktop geometry to use.
#GEOMETRY="<WIDTH>x<HEIGHT>"
#GEOMETRY="800x600"
GEOMETRY="1024x768"
#GEOMETRY="1280x1024"

# The name that the VNC Desktop will have.
NAME="my-vnc-server"

OPTIONS="-name ${NAME} -depth ${DEPTH} -geometry ${GEOMETRY} :${DISPLAY}"

. /lib/lsb/init-functions

case "$1" in
start)
log_action_begin_msg "Starting vncserver for user '${USER}' on localhost:${DISPLAY}"
su ${USER} -c "/usr/bin/vncserver ${OPTIONS}"
;;

stop)
log_action_begin_msg "Stoping vncserver for user '${USER}' on localhost:${DISPLAY}"
su ${USER} -c "/usr/bin/vncserver -kill :${DISPLAY}"
;;

restart)
$0 stop
$0 start
;;
esac

exit 0

My Observation about angstrom distribution

When I use the image BBB-eMMC-flasher-2013.06.20.img to put it on the microSD card with win32DiskImager, I see (from plugging SD in Ubuntu) the microSD card has 2 partitions 

eMMC-Flasher  -ext4
BEAGLE_BONE - vfat

where eMMC-Flasher contains an ubuntu data and BEAGLE_BONE contains only 4 files. 

ID.txt - just one line
MLO - 98K binary
u-boot.img - 371K binary
uEnv.txt - just one line

Flashing is done by pressing the 'Boot' button while connecting the power. It took 1 hour in my case when I flashed BBB-eMMC-flasher-2013.06.20.img.

However, once the microSD is flashed to eMMC, the 'eMMC-Flasher' partition will be gone and 'BEAGLE_BONE' partition is changed to include 3 new folders- App, Docs and Drivers AND some new files - START.htm, autorun.inf, README.md.

Android OS

Books

  • Bad to the Bone: Crafting Electronics Systems with Beaglebone and BeagleBone Black
  • Getting Started with BeagleBone: Linux-Powered Electronic Projects With Python and JavaScript Chapter 4: blinking leds. Chapter 5: Python pin control (GPIO, Analog input, Analog output). Chapter 6: Putting Python projects Online.
  • Beaglebone Home Automation. Chapter 2: Input and Output (including Adafruit python library). Chapter 3: Creating the Client and Server Applications (python). Chapter 4: Extending Server Capabilities (defining own beaglebone protocol, Python, light sensor, temperature sensor, transistor). Chapter 5: Motion detect and Camera cape in Python. Chapter 6: Creating Android client. Appendix (Boot time kernel traces, I2C, SPI)
  • Beaglebone Robotic Projects (based on BBB). Chapter 2: Programming (python and C++). Chapter 3: Speech Input and Output (microphone & speaker). Chapter 4: See (USB camera). Chapter 5: Wheel movement. Chapter 6: Legged movement. Chapter 7: Avoid obstacles by using sensors. Chapter 8: remote control of your robot (LCD cape, USB keyboard, python). Chapter 9: GPS. Chapter 10: whole system.
  • Programming the BeagleBone Black: Getting Started with JavaScript and BoneScript by Simon Monk.

BBB vs Raspberry Pi

Beaglebone 101

Angstrom includes a web server running on BBB. The web address is http://192.168.7.2

I have created screenshots in Google drive http://goo.gl/o03iex

Fix date/time

See here. Run the following to change the country and time zone. 

sudo dpkg-reconfigure tzdata

Then run 

sudo ntpdate pool.ntp.org

Increase sudo timeout

http://ubuntuforums.org/showthread.php?t=183418 

sudo visudo
# Add the following line for 10 minutes. Use -1 for infinity.
# Modify USER_NAME for your own.
Defaults:USER_NAME timestamp_timeout=10

Run Graphical App on remote computer

Suppose we have a Qt app we want to launch from a local computer and show the GUI on BBB. We can

  1. Run xhost + as a user on BBB
  2. Run export DISPLAY=:0.0 then our own graphical application from the local computer.

To run xhost command at boot (The xhost command needs an active X server to run, it can run at the login screen e.g. when lightdm loads), we can follow the instruction here

Run Graphical App as root on local computer

This is related to the question: Make X11 program work in an ssh sudo session

One way that works is to run ssh -X [email protected] first (it seems not necessary to use ssh -Y option). Then 

sudo XAUTHORITY=/home/debian/.Xauthority /home/debian/Downloads/servo/servo

Then my GUI app located in /home/debian/Downloads/servo/servo will be launched as root shown in my local machine.

If the GUI app is not run by root, we don't need to bother the xauthroity. We can just run the app.

Use microSD as ext storage

It is possible. See the idea in here.

Build R on BBB

I am using Ubuntu 13.04 image since angstrom linux missing many required packages.

Since the space is limited, instead of using 'sudo apt-get build-dep r-base', I manually install the essential packages: build-essential, gfortran, libreadline6-dev, libx11-dev, libxt-dev and openjdk-7-jre.

I am using R 3.0.1. (Update) R 3.1.0 works well too. 

ubuntu@ubuntu-armhf:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/mmcblk0p2  1.8G  276M  1.4G  17% /
none            4.0K     0  4.0K   0% /sys/fs/cgroup
devtmpfs        248M  4.0K  248M   1% /dev
none             50M  220K   50M   1% /run
none            5.0M     0  5.0M   0% /run/lock
none            248M     0  248M   0% /run/shm
none            100M     0  100M   0% /run/user
/dev/mmcblk0p1 1004K  472K  532K  48% /boot/uboot

sudo apt-get update
sudo apt-get install build-essential gfortran libreadline6-dev libx11-dev libxt-dev
sudo apt-get install openjdk-7-jre    
// (optional) need it if we don't want to get an error message at the end of running 'make'
// This require 143MB space.

// The whole process (configure + make) takes at least 2 hours on BBB
./configure --enable-R-shlib
make
// make > ~/Rmake.txt 2>&1

There is still warnings with library/datasets
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=695411
It seems this is false alarm.

ubuntu@ubuntu-armhf:~/R-3.0.1$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/mmcblk0p2  1.8G  1.1G  615M  64% /
none            4.0K     0  4.0K   0% /sys/fs/cgroup
devtmpfs        248M  4.0K  248M   1% /dev
none             50M  224K   50M   1% /run
none            5.0M     0  5.0M   0% /run/lock
none            248M     0  248M   0% /run/shm
none            100M     0  100M   0% /run/user
/dev/mmcblk0p1 1004K  472K  532K  48% /boot/uboot

The complete process of running ./configure and make are recorded in

Other configure options

http://cran.r-project.org/doc/manuals/R-admin.html#Configuration-on-a-Unix_002dalike 

./configure --disable-byte-compiled-packages --enable-R-shlib

Performance Test

Qt cross compile

The list below is specific to beaglebone (black)

Other resource related to Raspberry Pi 

sudo apt-get install gcc-arm-linux-gnueabi

What's wrong when running a binary created on x86_64 OS

For the hello world example, I will get an error in BBB if I just scp the binary file from x86_64 OS to BBB. 

debian@beaglebone:~$ ./a.out
-bash: ./a.out: cannot execute binary file

What we should do to compile hello.c

arm-linux-gnueabi-gcc -march=armv7-a -mtune=cortex-a8 -mfpu=neon -o hello hello.c
scp hello [email protected]:

Then we run hello program in BBB. It should run successfully.

http://www.valvers.com/embedded-linux/beaglebone/step06-cross-compiling

What we should do to compile hello.cpp

Note: do not install g++-arm-linux-gnueabihf package. It will give me the following error when I try to compile a simple cpp program. 

warning: ld-linux.so.3, needed by /usr/lib/gcc/arm-linux-gnueabihf/4.6/libstdc++.so, not found (try using -rpath or -rpath-link)

According to the above website or michaelhleonard.com we shall install the toolchain 

sudo apt-get install gcc-arm-linux-gnueabi
sudo apt-get install g++-arm-linux-gnueabi

I can build hello.cpp on my x86_64 host. 

arm-linux-gnueabi-g++ -march=armv7-a -mtune=cortex-a8 -mfpu=neon -o hellocpp hello.cpp

But when I run the hellocpp program, I get the following error 

debian@beaglebone:~$ ./hellocpp
./hellocpp: error while loading shared libraries: libstdc++.so.6: cannot open shared object file: No such file or directory

I also try the following. It is a big download but still does not help. 

sudo apt-get install ia32-libs

Some people suggested to add the following when compiling your program 

-static -static-libstdc++

It works!!! The complete compile command is (-static-libstdc++ is not necessary) 

arm-linux-gnueabi-g++ -march=armv7-a -mtune=cortex-a8 -mfpu=neon -static -o hellocpp hello.cpp

Linaro Toolchain

Although there are different toolchains, we are particularly interested in linaro toolchain. See https://wiki.linaro.org/WorkingGroups/ToolChain/FAQ.

Check out this page http://www.elinux.org/Toolchains for more information about toolchain.

Some paths

  • arm-linux-gnueabi-gcc, arm-linux-gnueabi-g++, arm-linux-gnueabi-ar,... are located at /usr/bin/. This can be found by typing arm-linux-gnuabi-[TAB]
  • ar, objcopy, strip also are located at /usr/arm-linux-gnueabi/bin.
brb@brb-P45T-A:~/Documents$ arm-linux-gnueabi-
arm-linux-gnueabi-addr2line  arm-linux-gnueabi-gprof
arm-linux-gnueabi-ar         arm-linux-gnueabi-ld
arm-linux-gnueabi-as         arm-linux-gnueabi-ld.bfd
arm-linux-gnueabi-c++filt    arm-linux-gnueabi-ld.gold
arm-linux-gnueabi-cpp        arm-linux-gnueabi-nm
arm-linux-gnueabi-cpp-4.6    arm-linux-gnueabi-objcopy
arm-linux-gnueabi-elfedit    arm-linux-gnueabi-objdump
arm-linux-gnueabi-g++        arm-linux-gnueabi-ranlib
arm-linux-gnueabi-g++-4.6    arm-linux-gnueabi-readelf
arm-linux-gnueabi-gcc        arm-linux-gnueabi-size
arm-linux-gnueabi-gcc-4.6    arm-linux-gnueabi-strings
arm-linux-gnueabi-gcov       arm-linux-gnueabi-strip
arm-linux-gnueabi-gcov-4.6   

brb@brb-P45T-A:~$ dpkg -L gcc-arm-linux-gnueabi
/.
/usr
/usr/share
/usr/share/doc
/usr/share/man
/usr/share/man/man1
/usr/bin
/usr/share/doc/gcc-arm-linux-gnueabi
/usr/share/man/man1/arm-linux-gnueabi-gcov.1.gz
/usr/share/man/man1/arm-linux-gnueabi-gcc.1.gz
/usr/bin/arm-linux-gnueabi-gcov
/usr/bin/arm-linux-gnueabi-gcc
brb@brb-P45T-A:~$ ls -l /usr/bin/arm-linux-gnueabi-gcc
lrwxrwxrwx 1 root root 25 Feb 18  2012 /usr/bin/arm-linux-gnueabi-gcc -> arm-linux-gnueabi-gcc-4.6
brb@brb-P45T-A:~$ locate arm-linux-gnueabi-gcc-4.6
/usr/bin/arm-linux-gnueabi-gcc-4.6
/usr/share/man/man1/arm-linux-gnueabi-gcc-4.6.1.gz

Configure Eclipse for cross compile

http://zombiebabylabs.com/2014/02/hello-beaglebone-world-a-c-primer/

GUI not shown up

http://www.marshut.com/xkshy/beaglebone-black-qt-gui-application.html

Cross compile Qt

Some possible options 

./configure -embedded arm -prefix /usr/local/QtEmbedded-arm -platform linux-g++ -little-endian -xplatform qws/linux-arm-g++ -qt-gfx-linuxfb -qt-gfx-vnc -qt-gfx-multiscreen -qt-mouse-pc -release -shared -no-fast -depths all -D QT_NO_QWS_CURSOR -confirm-license -no-pch

# http://www.cloud-rocket.com/2013/07/building-qt-for-beaglebone/
# based on qt 4.8.5
./configure -v -opensource -confirm-license -prefix /opt/qt -embedded arm -platform qws/linux-x86-g++ -xplatform qws/linux-am335x-g++ -depths 16,24,32 -no-mmx -no-3dnow -no-sse -no-sse2 -no-glib -no-cups -no-largefile -no-accessibility -no-openssl -no-gtkstyle -qt-mouse-pc -qt-mouse-linuxtp -qt-mouse-linuxinput -plugin-mouse-linuxtp -plugin-mouse-pc -fast -little-endian -host-big-endian -no-pch -no-sql-ibase -no-sql-mysql -no-sql-odbc -no-sql-psql -no-sql-sqlite -no-sql-sqlite2 -no-webkit -no-qt3support -nomake examples -nomake demos -nomake docs -nomake translations

# http://armsdr.blogspot.com/2014/01/bare-metal-qt-52-on-beaglebone-black_10.html
# Based on qt 5.2.0
# # qwx is located at mkspecs/qws. What does platform and xplatform do? 
./qt-everywhere-opensource-src-5.2.0/configure -v -opensource -confirm-license -prefix /usr/local/qt-5.2 -no-largefile -no-accessibility -qt-zlib -no-gif -qt-libpng -qt-libjpeg -no-nis -no-cups -xplatform linux-linaro-gnueabihf-g++ -device linux-beaglebone-g++ -device-option CROSS_COMPILE=/usr/local/linaro/bin/arm-linux-g
nueabihf-
  1. qws

QWS is a window server similar to X11 that works independently from it. Unlike X11, QWS windows cannot be forwarded to your Windows machine and will be displayed by your board directly. Before we proceed with starting our application in QWS mode ensure that your board is showing the text terminal and not the X11 session (press Ctrl-Alt-F1 to switch to it):

Native build Qt on BBB

The following screenshot demonstrates running qt-4.8.5/examples/painting/basicdrawing/ in BBB. That is, it is possible to compile the Qt directly in beaglebone black without using cross-compile.

BBB Qt drawing.png

For general instruction of building Qt on different platforms, consult to http://qt-project.org/doc/qt-4.8/installation.html.

The way I build Qt is 

mv qt-everywhere-opensource-src-4.8.5 qt-4.8.5
cd qt-4.8.5
./configure -v -opensource -confirm-license -no-largefile -no-accessibility -qt-zlib -no-gif -qt-libpng -qt-libjpeg -no-nis -no-cups -no-pch
make
sudo make install
  • configure takes about 1 hour. Not much information is given after running configure. It only said Qt is now configured for building. Just run 'make'. Once everything is built, you must run 'make install'. Qt will be installed into /usr/local/Trolltech/Qt-4.8.5. To reconfigure, run make confclean and configure.
  • Running make will take ~ 20 hours
  • Running sudo make install is quick (~ 5 minutes)
  • The std output shows /usr/local/Trolltech/Qt-4.8.5 is created
  • If we want to save (a little) time when running make, we can add -nomake examples -nomake demos to your configure invocations (I don't see these options in Qt 4.8), it works on both windows and linux. It still took ~18 hours when I build Qt 4.8.6.

It is interesting to compare the qt directory under $HOME and /usr/local/Trolltech. Note that even bin directory is copied to /usr/local, the contents inside bin folder are different (not shown here) 

debian@beaglebone:~$ ls qt-4.8.5/
bin              configure      imports             LICENSE.FDL   plugins       templates
changes-4.8.5    configure.exe  include             LICENSE.GPL3  projects.pro  tools
config.profiles  demos          INSTALL             LICENSE.LGPL  qmake         translations
config.status    doc            LGPL_EXCEPTION.txt  Makefile      README        util
config.tests     examples       lib                 mkspecs       src

debian@beaglebone:~/qt-4.8.5$ ls /usr/local/Trolltech/Qt-4.8.5/
bin    doc       imports  lib      phrasebooks  q3porting.xml  translations
demos  examples  include  mkspecs  plugins      tests

debian@beaglebone:~/qt-4.8.5$ ls /usr/local/Trolltech/Qt-4.8.5/examples/
animation    draganddrop            help       mainwindows   qtestlib      threads    widgets
dbus         effects                helper     multimedia    README        tools      xml
declarative  examples-manifest.xml  ipc        network       richtext      touch      xmlpatterns
designer     examples.pro           itemviews  opengl        script        tutorials
desktop      gestures               layouts    painting      sql           uitools
dialogs      graphicsview           linguist   qtconcurrent  statemachine  webkit
debian@beaglebone:~/qt-4.8.5$

The final step is to change PATH environment variable by nano .profile 

export PATH=/usr/local/Trolltech/Qt-4.8.5/bin:$PATH

Logout and login again to see if qmake is available.

We can write a simple Qt code to test. See here for the code and how to use command line to compile the code.

It is also interesting to see the gcc version on BBB (v4.6.3) 

debian@beaglebone:~$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/arm-linux-gnueabihf/4.6/lto-wrapper
Target: arm-linux-gnueabihf
Configured with: ../src/configure -v --with-pkgversion='Debian 4.6.3-14' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.6 --enable-shared --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --enable-objc-gc --disable-sjlj-exceptions --with-arch=armv7-a --with-fpu=vfpv3-d16 --with-float=hard --with-mode=thumb --enable-checking=release --build=arm-linux-gnueabihf --host=arm-linux-gnueabihf --target=arm-linux-gnueabihf
Thread model: posix
gcc version 4.6.3 (Debian 4.6.3-14) 

debian@beaglebone:~$ ls /usr/bin/arm*
/usr/bin/arm-linux-gnueabihf-cpp      /usr/bin/arm-linux-gnueabihf-gcc-4.6
/usr/bin/arm-linux-gnueabihf-cpp-4.6  /usr/bin/arm-linux-gnueabihf-gfortran
/usr/bin/arm-linux-gnueabihf-g++      /usr/bin/arm-linux-gnueabihf-gfortran-4.6
/usr/bin/arm-linux-gnueabihf-g++-4.6  /usr/bin/arm-linux-gnueabihf-run
/usr/bin/arm-linux-gnueabihf-gcc

Qt examples

Some great examples to try include

  • examples/animation/appchooser
  • examples/animation/states
  • examples/dialogs/extension
  • examples/dialogs/licensewizard
  • examples/effects/lighting
  • examples/effects/blurpicker
  • examples/graphicsview/weatheranchorlayout
  • examples/graphicsview/elasticnodes
  • examples/graphicsview/diagramscene (a working app for drawing diagrams)
  • examples/help/simpletextviewer (including image on help)
  • examples/help/ipc/ (networking)
  • examples/itemviews/chart (when a cell is selected, the corresponding text from another item list will be highlighted)
  • examples/itemviews/dirview
  • examples/itemviews/frozencolumn
  • examples/itemviews/pixelator
  • examples/itemviews/puzzle (Game)
  • examples/layouts/dynamiclayouts (widgets location changed at real time)
  • examples/network/bearermonitor (show all networks in a tree on lhs and status on rhs)
  • examples/network/fortunateclient
  • examples/network/http (download from an address)
  • examples/network/loopback (with progress bar for sent and receved packets)
  • examples/network/qftp (show contents in the textEdit. Cool!)
  • examples/network/securesocketclient (allow input)
  • examples/opengl (seems not working)
  • examples/painting/concentriccircles (for fun)
  • examples/painting/basicdrawing (basic test)
  • examples/painting/painterpaths (fill gradient on different shapes or letters)
  • examples/qtconcurrent/wordcount (becomes a background job running)
  • examples/richtext/calendar
  • examples/richtext/orderform
  • examples/script/helloscript (not sure about what 'script' means)
  • examples/statemachine/trafficlight
  • examples/statemachine/twowaybutton (very simple)
  • examples/statemachine/rogue (text game. How does it do it)
  • examples/statemachine/pingpong (nothing show up on BBB)
  • examples/threads/waitconditions (nothing show up on BBB)
  • examples/tools/inputpanel (auto pop up input panel from an empty box)
  • examples/tools/settingeditor
  • examples/uitools/textfinder (can highlight text)
  • examples/widgets/styles (use an image as background)
  • examples/widgets/stylesheet (no image was used)
  • examples/widgets/softkeys (no binary)
  • examples/widgets/digitclock (simple)
  • examples/widgets/calculator (classical)
  • examples/widgets/charactermap (magnifier on mouse-over character)
  • examples/widgets/codeeditor (highlight current line)
  • examples/widgets/lineedits (contain license key input with format hint)
  • examples/widgets/sliders (change widgets location at run time)
  • examples/widgets/tablet (manipulate image)
  • examples/widgets/tetrix (a game that works)
  • examples/widgets/tooltip (tooltip on shapes created at run time)
  • examples/xmlpatterns/trafficinfo (not working but background is cool)
  • examples/xmlpatterns/schema (specify a background color on a textEdit is effective)

Python + Qt

sudo apt-get install python-qt4

Create Qt application by using examples from http://zetcode.com/gui/pyqt4/

We can launch the application by one of 3 ways

  • Run it directly in BBB and the app is shown on BBB too
  • ssh -X [email protected] from host machine and run the app from there. The GUI will be shown on the host machine.
  • ssh [email protected] from host machine. Issue export DISPLAY=:0.0 and run the app from there. The GUI is shown on BBB.

GPIO Projects

Use terminal to access GPIO pins

Google: beaglebone black gpio /sys/class/gpio 

root@beaglebone:/sys/class/gpio# ls -l
total 0
--w------- 1 root root 4096 Dec 31  1999 export
lrwxrwxrwx 1 root root    0 Dec 31  1999 gpiochip0 -> ../../devices/virtual/gpio/gpiochip0
lrwxrwxrwx 1 root root    0 Dec 31  1999 gpiochip32 -> ../../devices/virtual/gpio/gpiochip32
lrwxrwxrwx 1 root root    0 Dec 31  1999 gpiochip64 -> ../../devices/virtual/gpio/gpiochip64
lrwxrwxrwx 1 root root    0 Dec 31  1999 gpiochip96 -> ../../devices/virtual/gpio/gpiochip96
--w------- 1 root root 4096 Dec 31  1999 unexport
root@beaglebone:/sys/class/gpio# echo 7 > export
root@beaglebone:/sys/class/gpio/gpio7# cat value
0
root@beaglebone:/sys/class/gpio/gpio7# cat direction
in
root@beaglebone:/sys/class/gpio/gpio7# echo low > direction
root@beaglebone:/sys/class/gpio/gpio7# cat direction
out
root@beaglebone:/sys/class/gpio/gpio7# echo high > direction

The LED lit up now. The 'value' is changed by the 'direction'.

/sys/class directory

debian@beaglebone:~$ cd /sys/class/
debian@beaglebone:/sys/class$ ls
arvo       graphics     lcd           pps          sound         usbmon
backlight  hidraw       leds          pwm          spidev        vc
bdi        hwmon        mbox          pyra         spi_master    video4linux
block      i2c-adapter  mdio_bus      rc           thermal       virtio-ports
bsg        i2c-dev      mem           regulator    timed_output  vtconsole
dma        input        misc          rtc          tty           watchdog
drm        isku         mmc_host      savu         ubi
dvb        kone         mtd           scsi_device  udc
firmware   koneplus     net           scsi_disk    uio
gpio       kovaplus     power_supply  scsi_host    usbmisc

GPIO interactive map

http://eskimon.fr/beaglebone-black-gpio-interactive-map. It can toggle available pins (40), HDMI pins (20), emmc2 pins (10), I2C2 pins (2), power related pins (13).

Onboard LEDs

$ ls /sys/class/leds/
beaglebone:green:usr0  beaglebone:green:usr1  beaglebone:green:usr2  beaglebone:green:usr3
## 'trigger' determines what event is monitored
$ ls /sys/class/leds/beaglebone\:green\:usr0/
brightness  device  max_brightness  power  subsystem  trigger  uevent
$ cat /sys/class/leds/beaglebone\:green\:usr0/trigger
none nand-disk mmc0 mmc1 timer oneshot [heartbeat] backlight gpio cpu0 default-on transient

## stop the heart
# echo none > /sys/class/leds/beaglebone\:green\:usr0/trigger

## turn LED on (no blinking)
# echo none > /sys/class/leds/beaglebone\:green\:usr0/trigger
# echo 1 > /sys/class/leds/beaglebone\:green\:usr0/brightness

## strobe LED (get BeagleBone's heart racing at 20 'beats' per second)
# echo timer > /sys/class/leds/beaglebone\:green\:usr0/trigger
# echo 25 > /sys/class/leds/beaglebone\:green\:usr0/delay_off
# echo 25 > /sys/class/leds/beaglebone\:green\:usr0/delay_on

## *whew* ... restore default heartbeat
# echo heartbeat > /sys/class/leds/beaglebone\:green\:usr0/trigger

4D LCD Cape

It is a cool add-on for BBB. See official web site

Tip: To remove full path from terminal, edit ~/.bashrc to replace "\w" with "\W". See for example askubuntu.com.

Qt + GPIO

Setting up an IO python library (GPIO, PWM, ADC, I2C, SPI, UART)

http://learn.adafruit.com/setting-up-io-python-library-on-beaglebone-black

  • PWM: P8_13, P8_34, P8_36, P8_45, P8_46, P9_14, P9_21, P9_22, P9_29, P9_42. Eg. blink LED, fading LED, servo.
  • ADC: P9_33, P9_35, P9_36, P9_37, P9_38, P9_39, P9_40. Eg. measure light, ultrasonic sensor, accelerometer, joystick, Potentiometer.
  • I2C: P9_19, PI_20. Eg. temperature/pressure sensors.
  • SPI: P9_17, P9_18, P9_21, P9_22, P9_28, P9_29, P9_30, P9_31.
  • UART: 17 pins.

Adding a push button

http://learn.adafruit.com/connecting-a-push-button-to-beaglebone-black

Measure light

http://learn.adafruit.com/measuring-light-with-a-beaglebone-black My example: 

import Adafruit_BBIO.ADC as ADC
import time
from time import localtime, strftime

sensor_pin = 'P9_40'

ADC.setup()

#print('Reading\t\tVolts')
print time.asctime(time.localtime(time.time())), '\tReading\t\tVolts'

while True:
    reading = ADC.read(sensor_pin)
    volts = reading * 1.800
    #print('%f\t%f' % (reading, volts))
    #print(strftime("%Y-%m-%d %H:%M:%S", localtime()))
    print time.asctime(time.localtime(time.time())), '\t%f\t%f' % (reading, volts)
    time.sleep(60)

which can be run (and the output was written to a file for logging) 

sudo python light.py > tmp.txt

If we want, we can follow the tutorial in here to have the light reading logged on the COMS or send to google docs like [1]. Alternatively, we can let BBB to send an email to you like here.

Fading RGB using PWM

http://learn.adafruit.com/fading-a-rgb-led-on-beaglebone-black/overview

Note that we don't have to use RGB led. We can just connect a single color led. But to use PWM, we cannot choose any pin we want. For example, p8_10 won't work. Below is a simplified example. Save it as fading.py and run it with sudo python fading.py. 

import Adafruit_BBIO.PWM as PWM
import time
red = "P8_13"
PWM.start(red, 0)
def fade(colorA):
    for i in range(0, 100):
	    PWM.set_duty_cycle(colorA, 100-i)
	    time.sleep(0.05) 
for j in range(10):
    fade(red)
PWM.stop("P8_13")
PWM.cleanup()

The led will fading using the above code. If we change line 7 to 

            PWM.set_duty_cycle(colorA, i)

the LED will grow. If we change line 9 to while True:, the process will continue until we hit Ctrl+C.

The duty cycle is the reverse of what you might expect: if you have an LED plugged in, a duty cycle of 0 will be brightest, 100 will be dimmest.

Blinking an LED

Do not use a lower value resistor than 470Ω. The outputs can only provide about 4mA and the resistor prevents too much current flowing and potentially damaging the BBB.

But on another project (fading rgb LED), it mentioned you can use 220Ω to 1KΩ resistors.

Note that we have to run sudo su before we work on python program for any gpio project.

http://learn.adafruit.com/blinking-an-led-with-beaglebone-black

To install the Adafruit_BBIO python library in Debian, use the following. See https://github.com/adafruit/adafruit-beaglebone-io-python 

sudo ntpdate pool.ntp.org
sudo apt-get update
sudo apt-get install build-essential python-dev python-pip -y
#easy_install -U distribute  //debian only
sudo pip install Adafruit_BBIO

The python example to blink LED is 

import Adafruit_BBIO.GPIO as GPIO
import time

GPIO.setup("P8_10", GPIO.OUT)

while True:
    GPIO.output("P8_10", GPIO.HIGH)
    time.sleep(0.5)
    GPIO.output("P8_10", GPIO.LOW)
    time.sleep(0.5)

Controlling a servo (PWM)

We can actually try the following simpler approach using bonescript without bothering a command line. Just open a browser tab and type the address http://beagleboard.org/Support/BoneScript/ServoMotor/. It just works (Angstrom Distribution, running using Bonescript from web)! Make sure to change P9_14 to whatever (eg P8_13) as needed.

The SG90 micro motor operators at 4.0 to 7.2 volts according to here although it works when I plug the power to A9 3.3V pin.

For some reason, the Adafruit python code does not work. The servo has a vibration but not turn. Not sure what needs to be changed.

I found we can control the servo using command line. See the post. Note that for my current Angstrom, I need to use pwm_test_P8_13.15. Also this folder is created only after I run the Bonescript. So the example code is (the pwm_test_P8_13.16 number may change from each run ??) 

// On my BBB, polarity is inverted by default
echo 0 > /sys/devices/ocp.2/pwm_test_P8_13.16/polarity

echo 20000000 > /sys/devices/ocp.2/pwm_test_P8_13.16/period 
echo 500000 > /sys/devices/ocp.2/pwm_test_P8_13.16/duty
echo 1 > /sys/devices/ocp.2/pwm_test_P8_13.16/run

Valid pulse width for "Tower Pro sg90" is 500-2400 µs, so valid values for "duty" are 500000-2400000.

The contents of the directory look like 

root@beaglebone:~# ls -lh /sys/devices/ocp.2/pwm_test_P8_13.14/
driver	duty  modalias	period	polarity  power  run  subsystem  uevent

A summary of tutorial is on http://forum.beaglefu.com/topic/59-quick-beaglebone-black-pwm-commands/. It is obtained from google: /sys/devices/ocp.2/pwm. As we can see, once the command line works, it is easy to wrap the code in other languages (python, c, et al). The full instruction is 

echo am33xx_pwm > /sys/devices/bone_capemgr.8/slots
echo bone_pwm_P8_13 > /sys/devices/bone_capemgr.8/slots
echo 20000000 > /sys/devices/ocp.2/pwm_test_P8_13.14/period 
echo 0 > /sys/devices/ocp.2/pwm_test_P8_13.14/polarity     # seems necessary
echo 2400000 > /sys/devices/ocp.2/pwm_test_P8_13.14/duty   # counter-clockwise
echo 500000 > /sys/devices/ocp.2/pwm_test_P8_13.14/duty    # clockwise 180 degrees
echo 1 > /sys/devices/ocp.2/pwm_test_P8_13.14/run          # start the fun
echo 0 > /sys/devices/ocp.2/pwm_test_P8_13.14/run          # stop the fun

I found this approach works on both Angstrom and Debian.

BBBservo.jpg

Dictionary

  1. Period: inverse of frequency
  2. Frequency: Eg period=1000 mS is about freq 1kHz while period=10 mS is about 100 kHz. If we push the frequency too high, a transient noise on the signals would be observed on the waveforms.
  3. Duty cycle: the unit is 0 to 1=(100%). What percent of time the signal is in high level.

Measuring temperature

http://learn.adafruit.com/measuring-temperature-with-a-beaglebone-black

HC-SR04 (5v) sonar sensor

http://www.youtube.com/watch?v=bssyOCcU_Q4

Connect to 5v device

See 3.2.4 of the book "Bad to the Bone".

Input voltage & voltage divider

http://beagleboard.org/Support/BoneScript/accelerometer/

PIR motion sensor (ADC)

http://beagleboard.org/Support/BoneScript/PIRMotionSensor

Pull-up Resistor

A very simple robot

http://beaglebone.cameon.net/beaglebone-robotics/1-robot-platform

I2C

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