7.5inch e-Paper display (H) works with Arduino R4 UNO, but not MEGA 2560

Other Hardware Displays
1

Hello there,

I have been pulling out my hair with this problem. So I have been using the following e-paper hardware:

This combination works fine for my Arduino UNO R4 Wifi. However, I cannot use that board because if I try to use the whole screen, I run into memory issues. So I changed it out with an Arduino MEGA 2560 R3. I am able to run the Waveshare provided example code and the GxEPD2 Example and HelloWorld and code on it, but nothing shows up on the screen - it remains stark white. Here are some things i tried to debug it:

  • Put the PWR pin to the 3.3V output to keep it on high - still doesn't work
  • Tested all the pins individually with a blinking LED - they all work

I am out of ideas - anyone have any ideas to solve this problem? Part of me is also contemplating sticking with the Arduino UNO R4 WiFi and getting an e-Paper Shield to deal with the memory issues but I am not sure if it is compatible with GxEPD

2

This is why showing a schematic is always a Good Idea. It prevents wasting time with basic questions like:

"Have you accounted for the fact that the SPI pins are not on pins 10-13 on the Mega?"

Oh, and

is a recipe for a dead display if that means you're supplying 3.3V power with 5V signals from the Mega.

Operating Voltage 3.3V / 5V (The IO level voltage must be consistent with the supply voltage)

3

Yes, I have - followed the Mega2560 schematic in https://www.waveshare.com/wiki/7.5inch_e-Paper_HAT_(B)_Manual#Working_With_Arduino exactly and still having problems.

As for the PWR, it is confusing - my VCC is always plugged into 5V. The PWR is generally plugged into D6 as shown in the link (which I did and it did not work) - this forum post suggested plugging it into 3.3V instead to keep the pin set to high but I also have no results from this suggestion

4

That's not a schematic. And that table is what someone else did. Which may or may not be what you did. And my trust of what I haven't been allowed to see is essentially zero.

But hey, I wish you good luck in figuring it out. With no schematic of what you've done, I'm done here.

5

I mean, I could create a schematic of the table above and you would still have no idea whether I even followed the schematic I provided unless you were with me in person? I did follow the MEGA 2560 table, double, tripled, quadrupled checked it and still no dice, hence why I am posting here - posting on a forum is a pretty last resort action for me. The only difference, as I mentioned, was switching between the PWR pin from D6 (which I tried and failed) to the 3.3V source (which I also tried and failed)

6

Is it really a Waveshare display?
Since when has a Mega2560 had more memory than a UNO R4 WIFI?