GxEPD2 support for GDEM075T42 display

Other Hardware Displays
1

Hi @ZinggJM,

I recently ordered a number of new displays of type GDEM075T42 (7.5 inch E-ink screen 800x480 Support fast update Partial update E-paper display GDEM075T42_GooDisplay, 7.5-Inch ePaper Screen 800x480 Resolution Lightning-fast 0.3s Partial Refresh Perfect for Smart Signs). Unfortunately I can't find that display in the list of displays supported by the GxEPD2 library.

I previously built a few projects using GxEPD2 library with a GDEY075T7 (E-ink screen 7.5 inch electronic paper display 800x480 GDEY075T7_GooDisplay, GooDisplay 7.5inch E Paper Screen Module 4-Grayscale E-Ink Display HAT 0.34s Refresh SPI Interface) display. I had used the GxEPD2_750_T7 class (instead of GxEPD2_750_GDEY075T7) which worked fine with the GDEY075T7 display. However when using that class with the GDEM075T42 display, the background is rendered too dark and it doesn't appear to refresh correctly.

When I attempted to look at the official sample code for GDEM075T42, it appeared to be identical to GDEY075T7 so I am unsure what needs to be changed to support this display.

2

Hi @anthonymorris13 ,

Please note that @ZinggJM has turned his back on the Arduino Forum, at least for now.
But Discussions are now enabled in GxEPD2.

You could try to disable useFastFullUpdate , or adapt the temperature value used:

void GxEPD2_750_GDEY075T7::_Update_Full()
{
  if (useFastFullUpdate)
  {
    _writeCommand(0xE0); // Cascade Setting (CCSET)
    _writeData(0x02);    // TSFIX
    _writeCommand(0xE5); // Force Temperature (TSSET)
    _writeData(0x5A);    // 90
  }
  else
  {
    _writeCommand(0xE0); // Cascade Setting (CCSET)
    _writeData(0x00);    // no TSFIX, Temperature value is defined by internal temperature sensor
    _writeCommand(0x41); // TSE, Enable Temperature Sensor
    _writeData(0x00);    // TSE, Internal temperature sensor switch
  }
  _writeCommand(0x12); //display refresh
  _waitWhileBusy("_Update_Full", full_refresh_time);
}
3

The GDEM075T42 is under EOL epd.
Most likely it is a precursor of the GDEY075T7 that doesn't have the waveform table for fast full refresh in OTP. So disabling fast full refresh use may help.

4

Thank you for your suggestions. I tried disabling useFastFullUpdate but that didn't help. Changing the temperature value did increase the brightness of white at some point but it also decreased the darkness of the black so didn't improve the overall contrast ratio.

Given the GDEM075T42 is EOL, I'm going to just try to replace them with GDEY075T7 which have worked for me in the past.

5

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