White screen issue

It is recommended to use newer firmware (1.0.0 or newer), since it is known to work with almost all non-defective HY28A/B SPI/parallel displays (given that the 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 causing a white screen, the EEPROM is simply not 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 firmware newer 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: In newer firmware touchscreen code uses the SPI bus for identifying activated touchscreens. 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 actions never took place on the SPI bus.