First, let me say thank you for all the contributions and suggestions which where contributed to the project GitHub Repository. It is great to see that this project sparks your interest and to learn about ways to improve it even further!
Based on this, a new revision of the board where developed (Actually there where two "Revisions" since the last project log, so this latest one is called "V4"). The main focus here was to be more power-efficient to enable battery-powered applications. To achieve that, two LT1945 converters are used to derive the necessary voltages instead of using additional linear regulators. This comes at the cost of more parts overall, however, the LT1945 chips are available cheaply from AliExpress and most additional parts are basic parts which should be available at many chap SMT assembly services. Additionally, a less power-hungry LDO is used to power the ESP32.
So overall, the improvements over revision V2 include:
- Deep sleep current of ~80uA if powered with 3.7V and the display attached. If the display is attached, deep sleep current rises to ~440uA and I am not quite sure why, yet. Any suggestions are welcome :)
If powered via 5V, unfortunately the p-channel mosfet which is used to gate the booster power might still turn on, which increases sleep current to ~340uA without display. This could be fixed in a future revision, but for most battery powered applications a lower voltage is used anyway.
- Slightly faster drawing (-80ms for a full 16bpp frame, -100ms for a clear cycle) at the expense of one broken-out output pin.
The PCB and updated firmware library are now available on GitHub!