Using Waveshare 4.2 E-Paper Display Module (B) on ESP32

[ReiettoAyanami]

Hi,
I'm new to using E-paper display and so I wanted to ask if it was possible to know if
this display was compatible with an esp32 and if it was possible to use it as an image displayer (even one at a time is good).
The official webstore: https://www.waveshare.com/4.2inch-e-paper-module-b.htm
My doubt for using this as an image displayer comes from this line in the official GxEPD2 library repo:
////#include "bitmaps/Bitmaps3c400x300.h" // 4.2" b/w/r // not enough code space
this is on line 137: GxEPD2/examples/GxEPD2_HelloWorld/GxEPD2_HelloWorld.ino
Even though it should only be a 15KB BMP image, no?
I already know it doesn't support partial refresh, and that's not a big deal, I just want to know
I'm using this ESP32-CH340 from AZ-Delivery.

Yesterday I tried with uncommenting line 280 in examples/GxEPD2_Example/GxEPD2_display_selection.h:
// GxEPD2_3C<GxEPD2_420c_Z21, GxEPD2_420c_Z21::HEIGHT> display(GxEPD2_420c_Z21(/*CS=5*/ SS, /*DC=*/ 17, /*RST=*/ 16, /*BUSY=*/ 4)); // GDEQ042Z21 400x300, UC8276
(old style)
And also tried uncommenting line 93 in examples/GxEPD2_Example/GxEPD2_display_selection_new_style.h
//#define GxEPD2_DRIVER_CLASS GxEPD2_420c_Z21 // GDEQ042Z21 400x300, UC8276, (hidden)

The wiring i'm using is described at line 74 in examples/GxEPD2_Example/GxEPD2_wiring_examples.h:
// BUSY -> 4, RST -> 0, DC -> 2, CS -> SS(5), CLK -> SCK(18), DIN -> MOSI(23), GND -> GND, 3.3V -> 3.3V // for use with Board: "ESP32 Dev Module":

I tried this the other day and worked, but after some testing it started displaying noise, I've already checked if it's a wiring issue and I'm pretty confident that it's not the case.

I'm now buying another display to check if it's a hardware-related issue, but for now some help would be really appreciated.
Thanks to anyone answering to this post.
Best Regards.

P.S
I'm using Adafruit_GFX not the GFX class provided by GxEPD2.
I've tried using the "new style" and "old style" for initializing the display, neither work after my second attempt, I've tried using the old style alone, and i can at least "talk" to the display, using the new style alone doesn't even initialize the display object for me.

[G6EJD]

You need to use the half-buffer variant/option

[G6EJD]

You'll need about 45K of free ram to build a 3-colour image, a lot will depend on your final source code s d how much ram is consumed by variables

[ReiettoAyanami]

Hi, sorry if I'm taking long, I had to deal with some work related stuff, and i also forgot that you told me to use the half sized buffer like an idiot so i was basically doing no progress.

[ReiettoAyanami]

Ok, I've tried them all, they don't even light up the display apparently, the most common serial output after booting is "Busy Timeout!".

[G6EJD]

OK, assuming you checked/amended the PIN numbers for each object changed. Both half and full buffer variants should work for that size screen and the GxEPD2 Hello World should be your test example.
Did you uncomment the correct driver object line and change the pin definition?
It is possible the display is faulty or the driver chip used is not yet supported by GxEPD2

[ReiettoAyanami]

I eventually bought one of the same display but just black and white, this one: https://www.waveshare.com/4.2inch-e-paper-module.htm
it's the same display, and I'm pretty sure the display is supported by the driver, so I can debug with it.
I will reach out tomorrow when it arrives and let you know if it works, unfortunately tonight I can't really do anything with the display.

[ZinggJM]

• you can select the display either in GxEPD2_display_selection.h or in GxEPD2_display_selection_new_style.h, but not in both at the same time.
• you need to make sure that the constructor parameters correspond to your wiring, or your wiring corresponds to the constructor parameters.
• line 74 of GxEPD2_wiring_examples.h is for the wiring of the 24pin FPC connector of a TTGO T8 ESP32-WROVER. The corresponding constructor line is line 221 of GxEPD2_display_selection_new_style.h.

You might test your display with the demo code of the Waveshare library https://github.com/waveshareteam/e-Paper. If the demo for your display is newer than the driver class in GxEPD2, then it may not be supported by GxEPD2, which seems to be the case: https://github.com/waveshareteam/e-Paper/tree/master/Arduino/epd4in2b_V2

[ReiettoAyanami]

Thanks! I'll take a look into it

[ReiettoAyanami]

One last question before I get flamed, is the waveshare spectra e6 supported?

[ZinggJM]

I could go searching. But you could as well provide a link!

[ReiettoAyanami]

Hi, so sorry, but I forgot, here's the link:
https://www.waveshare.com/4inch-e-paper-hat-plus-e.htm?sku=27367
Wiki

I'm pretty sure it's the same this display from Good-Display, but I'm not so confident about it...

EDIT:
I'm also pretty conscious about the fact that it's a full color display and it wouldn't be ideal for an ESP32's memory space(? Correct me if i'm wrong), so i might just ask.

[ZinggJM]

No, unfortunately it is not supported. Take a look at either the list in https://github.com/ZinggJM/GxEPD2/blob/master/README.md, or the selectable display drivers in GxEPD2_display_selection_new_style.h.

I also think it is the same display.

The memory space is not an issue. GxEPD2 supports paged display. It uses some trick to cope with the missing partial window addressing.