A script to automatically print out a Raspberry Pi's IP address on a connected SenseHAT when the device boots up.

graph TD
  boot("System boot")
  wait("Wait for IP\nShow 'no connection' icon")
  stop("Give up :(")
  show("Scroll IP address")
  user("User detected\nDormant")
  quiet("Quiet")
  
  boot --> wait
  wait -. "Timeout (3min)" .-> stop
  wait -- "IP assigned" --> show
  show == "SSH connected" ==> user
  show == "HDMI connected" ==> user
  user -- "Disconnected" --> show
  show -. "Timeout (3min)" .-> quiet
  show == "Joystick" ==> quiet
  quiet == "Joystick" ==> show

In the "dormant" state, nothing will be shown until all indicators of user presence are gone.

In the "quiet" state, a joystick middle-click event will reset the 3-minute timeout on the IP address scrolling across the screen. Any other joystick event will just show the IP once.

As root:

1. Move boot_sense_ip.py into your Pi's /etc/ directory (do not set the executable bit on it)
2. Edit /etc/rc.local to include this line: /usr/bin/env python3 /etc/boot_sense_ip.py &

If you need to kill the process that started at boot, use ps aux | grep python to find the offending process, usually running as root.

You can also run this script manually like any normal python script. There are a handful of command line flags useful for testing and debugging without forcing a reboot, run with -h to get a usage message.

Optional improvements to your rc.local file:

1. Have it log output to a file: exec 1>/tmp/rc.local.log.$$ 2>&1 (print with tail /tmp/rc.local.log.*)
2. Print the background job's ID after it's spawned: jobs -p