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Raspberry Pi as Slideshow / Digital Signage Server

Because of its lean and fan less design the Raspberry Pi is a perfect piece of hardware to create a simple slideshow system or so called Digital Signage Server (DSS). Perfect to drive a LCD somewhere to teaser the latest offers or new products.

Introduction

It doesn’t matter what kind of Raspberry Pi we use It works with all versions quite well. First we need to install Raspbian on the Pi. We can use a Raspbian Image or the NOOB SD-Card the choice is yours. Images can be found at https://www.raspberrypi.org/downloads/

After the Pi is connected to a screen, keyboard and mouse we insert the SD-Card and power it up.

Installation

The installer wants to know if we want to use the GUI or the console. We keep booting into the console. All other questions can be answered with the default answers. We set the network settings to fit our network.

Right after the first reboot we login with our Pi User and use the raspi-config tool to activate the ssh daemon.

There are some packages we need to install manually.

apt-get install x11-xserver-utils feh

Deactivate energy saving mode

In the default setting, the screen is turned of after a couple of minutes. To always display our slide show we have to turn this feature off. To do that we insert the following settings right after the second line of /etc/X11/xinit/xinitrx.

xset s off
xset -dpms
xset s noblank

New user

We create a new user to be used as the slide show user. With this account we’ll also upload the images to be displayed. This user will be automatically logged in after the Pi is started. For now we call it newuser.

adduser newuser

We write down the password. A public key setup may be used as well of course.

Autologin

To enable autologin after each reboot we’ll edit /etc/inittab and lookup the following line.

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

We change that to:

#1:2345:respawn:/sbin/getty 115200 tty1 
1:2345:respawn:/bin/login -f newuser tty1 /dev/tty1 2>&1

Next we’ll make another change to /etc/rc.local and add right before exit 0 a new line:

su -l newuser-c startx
exit 0

Now XServer is started with our new user.

With the next reboot the GUI should be started with user newuser.

The feh slide show script

In the newusers home directory we create the following script:

#!/bin/bash 
FOLDER="Desktop/Pictures/"
TEMPF="/tmp/slideshow";
export DISPLAY=":0"

if [ -d $FOLDER ]
then
MD5C=$(ls -al $FOLDER | md5sum | awk '{ print $1 }');
else
echo "Error: Folder does not exist";
fi;

case $1 in
start)
feh --quiet -Z -F -Y --slideshow-delay 12 $FOLDER &
echo $MD5C > $TEMPF
;;
stop)
pgrep -f "feh" > /dev/null && kill `pgrep -f "feh"` && rm $TEMPF
;;
restart)
$0 stop && $0 start
;;
status)
if [ $(pgrep -f "feh") ]
then
echo "Slideshow running";
exit 0;
else
echo "Slideshow not running";
exit $?
fi
;;
cron)

if [ -e /tmp/slideshow ]
then
MD5O=$(cat /tmp/slideshow)
if [ $(pgrep -f "feh") ]
then
# Passt            true
else
$0 start;
fi
else
echo "Slide show not started or $TEMPF vanished"
exit 0
fi

# Changes made = restart       if [[ $MD5O != $MD5C ]]
then
echo $MD5C > /tmp/slideshow
$0 stop
$0 start
exit 0
fi
;;
*)
echo "Usage: $0 {start|stop|reload|cron}";
exit 2
;;

esac

The script supports four parameters: start, stop, restart and cron. Start and Stop we can use right now. If there are some pictures in Desktop/Pictures and we call the script with start the slide show should start right away. If needed we can change the delay right in the script.

The Script should be put into the cron table with parameter cron. This way it’ll check if there are new or changed images and if necessary restart the slide show.

To start the slide show right away we create a small autostart file for our window manager LXDE.

[Desktop Entry]
Name=Slideshow
Exec=/home/newuser/slideshow.sh start
Terminal=false
Type=Application

After the next reboot the slide show should start right away. The following cron entry will check for new files. We use crontab -e to edit the file.

* * * * * /home/newuser/slideshow.sh cron

This is about it.

 

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