Pimoroni's Badger2040 is a nice "intelligent" e-paper display with an integrated RP2040.
The design-decision that a Badger2040 needs a button-press to wake up when running from battery prevents any time-based applications which go to sleep and then wake up using a timer.
A small hardware-hack solves the problem if you can do without one of the buttons. For time-based applications (think "clock") this is usually the case.
You have two options:
- solder a small wire across the barely visible legs of one of the front buttons, or
- keep one of the buttons permanently pressed
The first option is best for a permanent solution, the second option works fine for test and development. If you have a case, you could also integrate the latter directly into it.
This repository contains the OpenSCAD design files (and STL) for a little 3D-printed clamp that implements the second option. The clamp is really small and prints within 4 minutes (PLA, 0.2mm layer hight).
Note that the permanently pressed button does not draw a relevant amount of current, especially compared to the current-draw of the RP2040 during sleep (6.8mA).