Problems with repaints

[bitboxer]

I got a Eink+ESP32 device as a present by a good friend. And now I am trying to make it work with my own software. The software that came with it renders stuff without any flickering. Redraws are instant and it does not do a flickering black screen till the image is fully rendered.

Now I tried to build my own code, but sadly it looks like I don't have enough embedded knowledge to make it fully work.

When I do partial updates, everything in the column and row outside the partial gets damaged, like so:

Luckily I was able to get this diagram of the device:

The example code of the screenshot can be found here:

https://gist.github.com/bitboxer/f383a8652f931cec688f5a37db27bc63

It would be super nice if someone here could help me figure this one out 🙏 .

[bitboxer]

Ah and on the back of the device I see the following marking if it helps:

kegm075004t08-v179c

[ZinggJM]

Is your display black/white or three colors?

If it is black/white, then you should use the b/w display class and a b/w driver class.

Your display may have a different controller than any of the 7.5" panels GxEPD2 supports.

[bitboxer]

Does it help that the chip is supposed to be a UC8179?

[ZinggJM]

Yes, good to know. There seem to be 3 controller names used by Good Display for the same or equivalent controller.

//#define GxEPD2_DRIVER_CLASS GxEPD2_750_GDEY075T7  // GDEY075T7  800x480, UC8179 (GD7965), (FPC-C001 20.08.20)
//#define GxEPD2_DRIVER_CLASS GxEPD2_750c_Z08 // GDEW075Z08  800x480, EK79655 (GD7965), (WFT0583CZ61)

But we still need to find out if the controller of your display has the wavetables in OTP.

I can draw Black and Red without problems, just the refreshing does not work correctly.

Its not clear to me what you mean by this.

I suggest you try with the example GxEPD2_Example and report the diagnostics from the Serial Monitor.
This will allow to check the BUSY active times against the values I added in comments in GxEPD2_750c_Z08.h.

[bitboxer]

Sorry for the delay, but now I was able to do this:

I used:

#define GxEPD2_DISPLAY_CLASS GxEPD2_3C

with

#define GxEPD2_DRIVER_CLASS GxEPD2_750c_Z08 

and

GxEPD2_DISPLAY_CLASS<GxEPD2_DRIVER_CLASS, MAX_HEIGHT(GxEPD2_DRIVER_CLASS)> display(GxEPD2_DRIVER_CLASS(/*CS*/ 5, /*DC=*/ 19, /*RST=*/ 16, /*BUSY=*/ 17))

Which hopefully is the correct way to wire it all up.

In the console I see this:

PowerOn : 125999
16:11:03.133 -> _Update_Full : 18476000
16:11:03.165 -> _PowerOff : 41000
16:11:04.290 -> _PowerOn : 126000
16:11:23.101 -> _Update_Part : 18477000
16:11:42.600 -> _Update_Part : 18477000
16:12:03.096 -> _Update_Part : 18478000
16:12:22.887 -> _Update_Full : 18477000
16:12:22.950 -> _PowerOff : 41000
16:12:24.074 -> _PowerOn : 126000
16:12:43.140 -> _Update_Part : 18478000
16:13:01.665 -> _Update_Part : 18480999
16:13:22.482 -> _Update_Full : 18478000
16:13:22.514 -> _PowerOff : 41000
16:13:23.637 -> _PowerOn : 126006
16:13:42.458 -> _Update_Full : 18478000
16:13:42.490 -> _PowerOff : 41000
16:13:43.618 -> _PowerOn : 126000
16:14:02.452 -> _Update_Full : 18478000
16:14:02.484 -> _PowerOff : 41000
16:14:03.614 -> _PowerOn : 126000

[bitboxer]

I can draw Black and Red without problems, just the refreshing does not work correctly.

Its not clear to me what you mean by this.

Sorry, i ment the partial repaint does not work as I would love to see. If I partially update something, it creates either black areas in the complete line/column or fades the whole line/columns.

[ZinggJM]

The refresh times reported are quite close to the times I had measured with my panel.
For 3-color refresh, partial and full refresh times are the same.
Ultra Chip controllers usually have partial in and partial out commands to restrict the refresh area. This doesn't seem to work correctly on your display. Maybe you have a different controller.

See also:

void GxEPD2_750c_Z08::refresh(int16_t x, int16_t y, int16_t w, int16_t h)
{
  // intersection with screen
  int16_t w1 = x < 0 ? w + x : w; // reduce
  int16_t h1 = y < 0 ? h + y : h; // reduce
  int16_t x1 = x < 0 ? 0 : x; // limit
  int16_t y1 = y < 0 ? 0 : y; // limit
  w1 = x1 + w1 < int16_t(WIDTH) ? w1 : int16_t(WIDTH) - x1; // limit
  h1 = y1 + h1 < int16_t(HEIGHT) ? h1 : int16_t(HEIGHT) - y1; // limit
  if ((w1 <= 0) || (h1 <= 0)) return;
  // make x1, w1 multiple of 8
  w1 += x1 % 8;
  if (w1 % 8 > 0) w1 += 8 - w1 % 8;
  x1 -= x1 % 8;
  _Init_Part();
  if (usePartialUpdate) _writeCommand(0x91); // partial in
  _setPartialRamArea(x1, y1, w1, h1);
  _Update_Part();
  if (usePartialUpdate) _writeCommand(0x92); // partial out
}

You could try to set usePartialUpdate false in the header file. Then the whole screen should flash, but display correctly.