E-ink display not set to sleep

[kimmobrunfeldt]

Writing this down so I don't forget, but the code doesn't set the e-ink display into sleep at the moment. The usb-it8951/main.c is used for updating the screen. There's no support for sending the sleep command.

Waveshare's C code has an example: https://github.com/kimmobrunfeldt/eink-weather-display/blob/main/rasp/IT8951-ePaper/Raspberry/lib/e-Paper/EPD_IT8951.c#L654 which should be ported to the usb-it8951 version to support sleep.

It's possible that after sending sleep mode, one must use some or all commands from the Init routine. I didn't investigate it further.

For my use-case this shouldn't matter AFAIK. The raspberry PI is awake only for ~30-60seconds, which means the display only gets power during that time. Theoretically it would be beneficial to set the EDP to sleep, to minimize the active time before power is cut, but that seems like a micro-optimisation.