Automation/RaspberryPi

The Raspberry Pi is an inexpensive Linux computer which you can for example use to play back videos (up to Full-HD). This page shows you how to set it up:

Making the RapberryPi run a video at startup

Prepare the system

Get a compatible and proven SD Card (make sure it is not a knock-off). Install The Raspbian image (NOOBS is okay for the beginning, but it wastes a bit space on the SDcard for the recovery image which we don't need. Copy the raspbian on the card. Read about #SD Card corruption issues to avoid those.

Once that is done, connect to the Internet (Ethernet + DHCP) and bring the OS up to date:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade
sudo apt-get install raspberrypi-net-mods

Then while we are at it we might want to check if the firmwarware is up to date too. "Firmware" is a bit confusing in this context as the raspberry apparently has no bios sitting on some chip, but all that "Firmware" is part of the stuff on the SD card. (Source)

uname -a

Will let us see the current version. Then there is a script we can run to update it.

sudo apt-get install git
wget https://raw.github.com/Hexxeh/rpi-update/master/rpi-update -O /usr/bin/rpi-update && sudo chmod +x /usr/bin/rpi-update
sudo rpi-update

Optional: If you need every little bit of space of the memory card you may want to remove some software and example content to free some memory.

sudo apt-get purge --auto-remove sonic-pi scratch squeak-vm idle idle3 timidity wolfram-engine  python-pygame penguinspuzzle dillo pistore

After all this we should re-boot

sudo reboot

Setup video playback

Test video playback: source

omxplayer /opt/vc/src/hello_pi/hello_video/test.h264

add option -r to change display frame rate and resolution to the one that the movie file has:

omxplayer -r /opt/vc/src/hello_pi/hello_video/test.h264

make a file startup_script.sh (shell script)

touch startup_script.sh
nano startup_script.sh

with the following content:

clear
echo "Automatic start up script running"
date '+Date %Y-%m-%d Time %H:%m'
echo -e "This is \c" && hostname
ifconfig | grep "inet addr"
sleep 2
clear
sudo shutdown -h +540 & omxplayer -r movie.mp4 --loop

sudo shutdown -h +540 will shut the Raspberry down in 9 hours.

You will have to make the file executable with

sudo chmod 775 startup_script.sh

and you can test if it works by running it

./startup_script.sh

Make it log in automatically

You don't want a password prompt when the raspberry boots source

Edit the inittab file.

sudo nano /etc/inittab

Disable the getty program. Find this line and comment it out by adding a # at the beginning of the line

#1:2345:respawn:/sbin/getty 115200 tty1

Add login program to inittab. Add the following line just below the commented line

1:2345:respawn:/bin/login -f pi tty1 </dev/tty1 >/dev/tty1 2>&1

This will run the login program with pi user and without any authentication

Save and Exit.

Make it start the script automatically:

sudo nano .bashrc

and right at the end put:

 if [ $(tty) == /dev/tty1 ]; then
   ./startup_script.sh
 fi

(that last 'if' makes sure the script is not starting in an x session)

HDMI Output

By default the RaspberryPi will check if HDMI is attached and switch video and audio output accordingly. This means you need to have the HDMI screen/projector switched on and connected before booting the Pi. Since this can be inconvenient (you may want to switch both on through the same multi-plug for example), you can also change this behaviour in the file /boot/config.txt

If you always want HDMI output, you would like to uncomment the lines

 hdmi_force_hotplug=1
 hdmi_drive=2

all of the switches are explained on elinux

Synchronizing multiple RaspberryPi

maybe you want to give the different Pi different host names, so you don't get confused. Do it in the config utility:

sudo raspi-config

install pexpect:

sudo apt-get install python-pexpect

install python bindings for DBUS

sudo apt-get install python3-setuptools
sudo wget https://github.com/LEW21/pydbus/archive/master.zip
sudo unzip master.zip
rm master.zip
cd pydbus-master/
sudo chmod 777 setup.py
sudo ./setup.py build
sudo ./setup.py install

sudo apt-get remove omxplayer
sudo rm -rf /usr/bin/omxplayer /usr/bin/omxplayer.bin /usr/lib/omxplayer
sudo wget -O- http://yokto.net/0/omxplayer/omxplayer-3176db4.tar.bz2 | sudo tar -C / -xjvf -
sudo ln -sf /lib/arm-linux-gnueabihf/libpcre.so.3 /lib/arm-linux-gnueabihf/libpcre.so.1
sudo wget -O /usr/bin/omxplayer-sync https://github.com/turingmachine/omxplayer-sync/raw/master/omxplayer-sync
sudo chmod 0755 /usr/bin/omxplayer-sync
sudo wget https://github.com/turingmachine/omxplayer-sync/raw/master/synctest.mp4

Make a local network, connect them with Ethernet cable (+Hub if more then two) and configure static IPs source

sudo nano /etc/network/interfaces

start on master:

omxplayer-sync -mubv synctest.mp4

start on slave:

omxplayer-sync -lubv synctest.mp4

-b flag to make screen background black. (Remove -v for verbose mode later once everything works)

Note: You can use the startup_script above to do this, just replace the omxplayer command with the omxplayer-sync command from here.

Timing

Set the time

dpkg-reconfigure tzdata

Note that the Raspberry doesn't have a real-time clock on board. Instead it saves the current time in a file when it shuts down and resumes at the same point when it boots. It is searching online for the current time when booting. If there is no Internet connection the time will almost certainly not be accurate! (Alternatively you could add a real-time clock shield or a GPS receiver which would allow you to get the current time without Internet connection)

Shut down at specific time

The shutdown command has a timer built in, so when it is called like this

sudo shutdown -h 15:00

the system will shut down at three in the afternoon.

sudo shutdown -h +30

will shut the system down in 30 minutes from now.

You can also set a cron job for shutting down on specific days at specific times.

sudo crontab -e

add this line:

45 18 * * * /sbin/shutdown -h now

to shut down 45mins past 6PM

source

SD Card corruption issues

It's a common problem when working with the Raspberry that the SD Card is getting corrupted and a boot fails. This is caused by not properly shutting down but cutting the power instead. When the raspberry is writing files to the scdard while the power is cut, the risk of SD Card corruption is high.

How to minimize the risk of SD Card corruption

• Also read: read-only-raspberry-pi
• Make sure it is a proven, compatible and non-fake SD Card
• A faster card may be more stable (shorter time to write - less times when it is dangerous when a power loss happens
• Never plug the cable, leave Raspberry always on
• Always shut down properly
• Equip Raspberry with a battery pack
• Use a read only file system
• Consider AlpineLinux instead of Raspbian

Backup and copy

let's say /dev/mmcblk0 is your card reader

make a backup of SDCard:

sudo dd if="/dev/mmcblk0" of="Pi.bin"

put backup on card:

sudo dd bs=4M if=Pi.bin of=/dev/mmcblk0

(both these commands take a long time and the terminal seems like frozen, there is no progress feedback)

Power

reboot:

sudo reboot -h

shutdown:

sudo shutdown -h now

Notes

other resources

Use multiple RasberryPis to make a video wall (needs one extra server-Pi, plus one Pi per client) Piwall