screen constantly flashing

[Lorrainbow]

Version: 2.5.47
Issue type: major bug
Hardware: elecfreaks (smaller screen)

Replicate

1. Turn on the shield.

BUG: The screen is flickering. I thought it was the microphone light flashing, but the screen is flickering as well.

[KierPalin]

I think we fixed this for both the JacdacDisplay and ST7735. Unforunately the fix caused the JacdacDisplay driver (but not the ST7735) to have some screen tearing when there's a lot of movement. This is only noticeable on the splash screen of a micro:bit-app when the 'MicroCode', 'MicroMusic', etc screen scrolls down. Nonetheless, we need to revisit the display-shield/screen/jddisplay.cpp code to fix it.

This is doubly important for pxt-arcade where the tearing is much more noticeable. After we fix jddisplay.cpp we should replicate the change in the equivalent pxt-common-packages library.