STM32 gotchas
148.Touchscreen flipped or does not work on 32F429IDISCOVERY

STM32F429 was the first STM32 to feature the LCD controller (LTDC) and SDRAM support (in FMC). The associated DISCO board - 32F429IDISCOVERY - showcases both these features, incorporating a 64-Mbit SDRAM and a 320x240 LCD display with resistive touchscreen.

This board proved to be quite popular and in almost 10 years it has seen several updates. These are marked on the board itself MB1075B through MB1075E (as of Jan 2023). UM1670 contains a list of changes in Board revision history chapter.

One of the changes involved swapping the YU/YD pins of the touchscreen. As a consequence, some versions of the board have swapped direction of the touchscreen as compared to others. This has been discussed here and here, those threads also contain links to firmware which can be used to test this phenomenon.

As the original touchscreen controller, STMPE811QTR, is not manufactured anymore, the boards are prepared to use a different controller, SX8651. This results in firmware which was written for the original controller, ceasing to work on boards with the newer controller.