Control Pico e-Paper 4.2B with ESP32-S3-Pico

[darkspirit510]

Hi all,

TLDR: Did anyone ever use GxEPD2 with a (probably/partly) non-matching SPI layout?

I have a Pico e-Paper 4.2 B. The Raspberry Pico does not provide enough RAM (or I am too lazy to optimze 😅), so I searched for a pin-compatible controller - and found it with the ESP32-S3-Pico. There is no official support in Arduino IDE. I guess it lacks real mappings for the pins, hence I tried ESP32-S3-Box and LOLIN S3, but without success.

The pin mapping is as follows:
Display Pin (Function according to Waveshare) -> ESP32 Pin (Function according to datasheet)
11: GP8 (DC) -> GP33 (FSPIHD)
12: GP9 (CS) -> GP34 (FSPICS0)
14: GP10 (SCK) -> GP35 (FSPID)
15: GP11 (MOSI) -> GP36 (FSPICLK)
16: GP12 (RST) -> GP37 (FSPIQ)
17: GP13 (BUSY) -> GP38 (FSPIWP)

So I see three options:

1. I'm misunderstanding the documentation and just have to use the correct constructor/setup/board selection (would love to hear this 😉)
2. I have to use software SPI
3. I have to solder wire bridges over my board

I already tried another ESP board with manual SPI wiring, using #define GxEPD2_DRIVER_CLASS GxEPD2_420c as constructor. This works, so the display is fine.
And yes, I saw this question. Sadly it uses the same e-paper, but another board with manual wiring.

Thank you in advance!

Sascha

[ZinggJM]

Hi @darkspirit510

You just need to call SPI.begin(SCK, MISO, MOSI, SS) before display.init(115200) to map HW SPI to your pins.
You can use any free pin for MISO; -1 also works.
See also line 186 in GxEPD2_Example/GxEPD2_Example.ino

[darkspirit510]

Hi @ZinggJM,

thank you for your reply. I didn't expect it to be THAT easy 😅 I wonder how I could miss this line. Thank you!

For anyone else looking for this exact question, here's what I've done:

1. In GxEPD2_Example.ino, add SPI.begin(35, -1, 36, 33) before display.init(115200)
2. Comment GxEPD2_display_selection_new_style.h#L21 and uncomment the following one
3. Uncomment GxEPD2_display_selection_new_style.h#L92
4. Change GxEPD2_display_selection_new_style.h#L221 to GxEPD2_DISPLAY_CLASS<GxEPD2_DRIVER_CLASS, MAX_HEIGHT(GxEPD2_DRIVER_CLASS)> display(GxEPD2_DRIVER_CLASS(34, 33, 37, 38));
5. Profit 💸