kimmobrunfeldt / eink-weather-display Goto Github PK

I'm not sure what the default is, but I didn't spot any used code that'd set the vcom value.
There's one reference to vcom value here https://github.com/kimmobrunfeldt/eink-weather-display/blob/main/rasp/usb-it8951/main.c#L179, but the function is not called anywhere. I'd guess that the original author tried to set it but continued with the default vcom value.

I have no idea what the real implications are if the vcom value is set to an incorrect one. My display cable suggested -1.15 (IIRC) as the value, the Python library had -1.5 as the default.

Waveshare wiki states:

Use the correct VCOM value

The VCOM value of each model of the e-paper is marked on the FPC cable. Make sure that you have used the correct VCOM value when you running the demo. Otherwise, the e-paper will deteriorate by working for a long time under the wrong VCOM value.

• Here's a Rust example of setting the vcom: https://github.com/adzialocha/it8951-video/blob/55c97852386f51e28581e72164d745f3a203c92c/src/api.rs#L345
• Waveshare C code example: https://github.com/kimmobrunfeldt/eink-weather-display/blob/main/rasp/IT8951-ePaper/Raspberry/lib/e-Paper/EPD_IT8951.c#L283

After updating the screen a few times, I noticed ghosting issues with the display. The previous temp could be seen very lightly.

Waveshare wiki has more info about the modes: https://www.waveshare.com/wiki/10.3inch_e-Paper_HAT

Also saving this mode reference PDF here: E-paper-mode-declaration.pdf

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.

Have you had it running long enough to be able to say anything about expected battery life other than the calculation you mention in the README based on theoretical use?

I liked the design of the weather display. Tell me how you can do it on a more budget ESP microcontroller or support Raspberry Pi Pico, as well as reduce the screen with support for 7.5 inch displays. And also enable support for Open Weather Map. It would be nice to add a BME280 temperature sensor to display the temperature and humidity in the room