Feature: Disable printer auto power-off, and enable power-on when plugged in

[rubin110]

Noticed that the printer occasionally turns itself off. It also doesn't turn itself back on when power is restored. A user must turn the printer back on, which isn't intuitive. Annoyingly these are settings exposed through their Windows driver. However digging around the brother_ql project, I found the following two commands which should do the trick...

Enable restore power after power loss:

echo -n -e '\x1b\x69\x55\x70\x00\x01' > /dev/usb/lp0

Disable auto power-off after timeout:

echo -n -e '\x1b\x69\x55\x41\x00\x00' > /dev/usb/lp0

The internet says once these are set they should persist through restarts. Unfortunately I don't have a way to read the settings back, so no idea if it sets after given the commands. Regardless it would be good to toss this into some sort of post start up script, maybe after the rpi has been online for ~15 minutes (given enough time for someone to plug in the printer if needed.

I don't know when I'll get to this, so I'm posting the task up here.

[rubin110]

Power restore mostly kinda works. If there are two rapid power offs/on it won't restore. Whatever. We'll see if the disable auto power off setting sticks.

[IllyaMoskvin]

Noticed that the printer occasionally turns itself off.

Does this happen when the printer is running via the RPi? (Versus being plugged into a dev machine, for example.)

Asking because I also noticed this issue, and I thought I fixed this via this script:

https://github.com/pumpingstationone/nametag-printer/blob/main/src/nametags/keepalive.py

This script runs in the background (vis supervisord) and queries the printer for status every 5 min.

From testing, this kept the printer from going to sleep overnight.

[Modifying the settings via echo to /dev/usb/lp0]

This is a great find! If it works, we can delete the keepalive script.