Create a service a timer

The goal here is to run a script that will select a random image and show it in the PIMORONI Inky Impression 7 Color ePaper every determined period of time. I assume python3 is already installed in the machine. The Pimorony Inky Impression libraries and examples can be downloaded from this website. I am using a Raspberry PI Zero WH with Raspbian GNU/Linux 11 (bullseye).

1. Install Pimoroni's Inky libraries (you may say YES to all).

   curl https://get.pimoroni.com/inky | bash
   

2. Go inside the directory where services are.

   cd /etc/systemd/system/
   

3. Create a the timer file.

   nano inky7.timer
   

   Add the following content to it:

   [Unit]
   Description=PIMORONI Inky Impression 7 color e-paper random image select and display TIMER.
   
   [Timer]
   OnUnitActiveSec=180s
   OnBootSec=180s
   
   [Install]
   WantedBy=timers.target
   

   Save and exit.
4. Create a the service file.

   nano inky7.service
   

   Add the following content to it:

   [Unit]
   Description=Description=PIMORONI Inky Impression 7 color e-paper random image select and display JOB.
   
   [Service]
   Type=oneshot
   SyslogIdentifier=inky7_service
   ExecStart=bash /usr/local/bin/inky7.sh
   

   Save and exit.
5. Create the script file.

   nano /usr/local/bin/inky7.sh
   

   Add the following content to it:

   ls /home/pi/Pictures/Inky/*.jpg | sort -R | tail -1 | while read file; do    python3 /usr/local/bin/show.py $file; done
   

   Save and exit.
6. Create the Python file.

   nano /usr/local/bin/show.py
   

   Add the following content to it (careful with the indentation):

   #!/usr/bin/env python3
   
   # File Name: show.py
   #
   # Usage 1: Show a selected image
   #
   #     python3 show.py foto1.jpg
   #     python3 show.py /home/pi/foto1.jpg
   #
   # Usage 2: Show a random image
   #
   #     ls /home/pi/*.jpg | sort -R | tail -1 | while read file; do    python3 show.py $file; done
   
   import time
   import sys
   
   from inky.inky_uc8159 import Inky, CLEAN
   
   from PIL import Image
   from inky.inky_uc8159 import Inky
   
   inky = Inky()
   
   saturation = 0.6
   
   # Clear display
   for _ in range(2):
       for y in range(inky.height - 1):
           for x in range(inky.width - 1):
               inky.set_pixel(x, y, CLEAN)
   
       inky.show()
       time.sleep(1.0)
   
   # Load image
   if len(sys.argv) == 1:
       print("""
   Usage: {file} image-file
   """.format(file=sys.argv[0]))
       sys.exit(1)
   
   image = Image.open(sys.argv[1])
   
   if len(sys.argv) > 2:
       saturation = float(sys.argv[2])
   
   inky.set_image(image, saturation=saturation)
   inky.show()
   

7. Reload the daemon to take the changes into account.

   systemctl daemon-reload
   

8. Start the timer, this will start the service automatically.

   systemctl start inky7.timer
   

9. Enable the timer so that it runs at startup, this is optional.

   systemctl enable inky7.timer
   

Example logs (journalctl):

Jan 23 20:38:49 raspberrypi systemd[1]: Starting Description=PIMORONI Inky Impression 7 color e-paper random image select and display JOB....
Jan 23 20:39:49 raspberrypi systemd[1]: inky7.service: Succeeded.
Jan 23 20:39:49 raspberrypi systemd[1]: Finished Description=PIMORONI Inky Impression 7 color e-paper random image select and display JOB..
Jan 23 20:39:49 raspberrypi systemd[1]: inky7.service: Consumed 22.214s CPU time.

Jan 23 20:42:49 raspberrypi systemd[1]: Starting Description=PIMORONI Inky Impression 7 color e-paper random image select and display JOB....
Jan 23 20:43:49 raspberrypi systemd[1]: inky7.service: Succeeded.
Jan 23 20:43:49 raspberrypi systemd[1]: Finished Description=PIMORONI Inky Impression 7 color e-paper random image select and display JOB..
Jan 23 20:43:49 raspberrypi systemd[1]: inky7.service: Consumed 22.266s CPU time.

Notes:
To stop the timer and the service respectively run:

systemctl stop inky7.timer
systemctl stop inky7.service

To stop running at startup run:

systemctl disable inky7.timer