@wsanders said in Paper S3 questions:
So I think we're stuck with ESP deep sleep for now. It would be interesting to see the code for the PMS150G. I'm not sure what all that FET logic around it is for, maybe an AXP192 wouldn't fit on the board. (And why a USB chip that would prevent the device from frying when plugged into a USB PM port wasn't included.)
Yeah, just like the OG M5Paper, the PaperS3 has a bunch of shortcomings that stem from, well, I don't want to say bad design... Just not properly thought through.
The PMS150G for example is OTP, so one can't change its behaviour. Using a slightly smarter, programmable MCU would've allowed for things like forwarding of interrupt signals based on logic, and deeper management of power states or their handling.
I would've also included the following changes:
Full quad SD data pins (there's enough free pins on the S3 according to the schematics)
separate MCU (like an RP2040 or similar low power MCU) for EPD handling, similar to how the M5Paper used the IT8951 (which itself was a mistake, as that MCU is super power hungry, and there was no way to reprogram it either), with open firmware, to offload display update tasks
USB hub controller so both the S3 and this EPDC MCU could be natively connected to a host for flashing/debugging
Better charge controller (the one used won't let the battery charge faster than 250mAh@5V, which is why you need to keep it on charger for hours).
Utilising the GT911 capacitive touch "buttons" similar to the ESP32-S3-BOX, with three or four zones available on the display bottom (fat) chin