pids - Digital Signage for the Raspberry Pi

What is this?

pids is a simple way to use a Raspberry Pi to display a slideshow, with little to no configuration needed. It's built on top of Raspbian and uses FIM to display images.

pids has been tested on both the Model 2B and Model 3B devices.

Running

• Download the latest image from https://pids.nsnw.ca/
• Uncompress and write the image to an SD card
• Plug in a USB storage device (such as a USB key) into a Pi, and boot it off the SD card
• Watch your image slideshow

NOTE: This is pretty alpha quality. It works, but I take no responsibility for any pain, suffering, destruction and/or disaster that may happen as a result. In particular, the configuration file is simply sourced from the attached USB device with zero sanity checks.

How does it work?

A small script (pids) runs on boot which does the following:-

• checks for the existence of device at /dev/sda, assuming it will be a USB storage device.
• mounts /dev/sda1 at /mnt/usb.
• checks for the existence of a optional configuration file (pids.conf) on the USB storage device.
• displays the images (using fim) on the USB storage device in a loop, and in a random order.

Prebuilt images are available (see https://pids.nsnw.ca/), or you can use the files in this repo to integrate it into your own image. The files are:-

• pids - the main pids script
• pids.service and pids-boot.service - unit files for systemd
• pids.conf - an example configuration that can be put on a USB storage device
• config.txt and cmdline.txt - modified configuration files that live in /boot

By default, both pids and the pids-boot service look for pids.png and pids-nousb.png in /usr/local/share/pids respectively. These are shown on boot (by pids-boot) and when no USB storage device is detected (by pids).

For config.txt and cmdline.txt, do not just copy these to your Pi's /boot directory. There may be options you have configured differently on your Pi, and this will overwrite them. Neither of these files are required to make pids work - they just set a few options to make it work better:-

• config.txt
  • disable_overscan=1 - this disables the black border around the screen. By default this is set to 0, so if you have problems with the output you can comment this line out.
  • disable_splash=1 - this disables any splash screens that Raspbian might display on boot.
• cmdline.txt
  • logo.nologo - this disables the Raspberry Pi logo that is displayed at the top of the screen on boot.
  • consoleblank=0 - this disables console blanking, which normally happens after a period of inactivity.
  • loglevel=1 - this configures the boot logging to only show important messages.
  • vt.global_cursor_default=0 - this disables the blinking cursor.
  • quiet - this quietens a few other things that might otherwise be displayed on boot.

Configuration

As mentioned above, pids will look for a configuration file on the attached USB storage device. The file it looks for is called pids.conf, and it will look for it in the root of the USB storage device.

This file can contain a few options:-

• INTERVAL, which tells fim how long to show each image for, in seconds. The default is 5 seconds.
• RANDOM, which tells fim whether to randomise the images. The default is 1 (enabling randomisation).
• QUIET, which tells fim whether to show details about each image. The default is 1 (enabling quiet mode).
• DISABLED, which tells pids to exit on boot and not run any further. The default is 0 (not disabled).
• SSH_KEY, which if specified should be an SSH key in the same format as found in ~/.ssh/authorized_keys. This will be placed into /home/pi/.ssh/authorized_keys on the Pi to allow login as the pi user.
• PERSISTENT, which tells pids to copy all the data off the USB storage device to allow subsequent reboots to happen without the USB storage device. The default is 0 (don't persist).
• URL, which if specified should be a URL pointing to a list of images for pids to download.
• REFRESH, which will cause pids to redownload the images from URL after the given number of seconds. By default this is not set, which means it will not redownload images until the next reboot.

By default, the pi user does not have a password set. This is to disable SSH login unless an SSH key is provided using the SSH_KEY option above. The only exception to this is if there's a problem on boot - for more information see the troubleshooting section below.

At the moment, only eth0 on the device is used, and it will attempt to configure itself via DHCP. Static network and wireless configuration is not yet supported, but is planned for a future release.

Troubleshooting

By default, the pi user does not have a password set. If one is set manually, it will be deleted again the next time the Pi is rebooted. This prevents remote logins as the pi user unless an SSH key is specified in the pids.conf file with the SSH_KEY option. However, if a USB storage device is not connected on boot or there is another problem, pids will set the password of the pi user to pids, allowing SSH login with this password.

pids itself is started on boot by systemd. The pids-boot service also runs, but much earlier in the boot process, to display the splash screen.

Right now, pids is hard-coded to look for /dev/sda. This means that if you have multiple USB storage devices connected, it will only use the first one.

Bugs, limitations and development

If you have any ideas for features, feel free to open an issue on GitHub and I'll take a look.

Copyright

The files in this repository are ©2019 Andy Smith (andy@nsnw.ca), and are released under the MIT License.