White screen issue

It is recommended to user newer firmware (1.0.0 or newer), since these are known to work with almost all non-defective HY28A/B SPI/parallel displays (given correct wiring is used) thanks to the support of the community.

In most cases white screen issues these days are coming from truly defective displays and/or incorrect wiring. Using the wrong EEPROM is no longer a problem for the display, it will simply not being used.

Please also check if the display communication settings of the display (SPI / parallel) matches the wiring on you mcHF. The board itself defaults to parallel mode, SPI needs some tweaking. However, most HY28B bought from eBay seem to be soldered for use with SPI. Displays bought in Chris' kit are configured for Parallel mode. Anyway, double checking never hurts, right?

If you want to use newer firmware than 0.219.24 AND do not use LCD HY28A in SPI mode you must remove R30...R32 on ui- board- otherwise you will get a white screen.

Reason is in newer firmware touchscreen code makes actions on SPI bus for identifying eventually activated touchscreen. This causes a bus error because R30...R32 short-circuit parallel and SPI bus.

In former versions of firmware the short-circuit doesn't matter because of never actions took place on SPI bus.

Another well known "white scree fault" is WHEN YOU HAVE 24LC01 mounted ... you can not squeeze an elephant in a shoe box hi hi ... the 24LC01 is way to small and so either do not use that eeprom at all (then the internal flash of mcu is used) ... or better use the right eeprom instead!