TFT Backlight Remains Off with 10.1 beta 1

[FoamyGuy]

CircuitPython version and board name

Adafruit CircuitPython 10.1.0-beta.1 on 2025-11-06; Adafruit Pybadge with samd51j19

Same behavior on PyGamer as well.

Behavior

After installing 10.1.0-beta.1 the TFT display remains dark when the device boots up. Reverting back to 10.0.3 makes the display go back to lighting up as normal.

Additional information

I tested PyPortal Titano (also SAMD) and it did not have this issue. Also tested FunHouse and it did not have the same issue either.

You can manually turn on the backlight with this code and then the screen is visible:

from digitalio import DigitalInOut, Direction, Pull
backlight = DigitalInOut(board.TFT_LITE)
backlight.direction = Direction.OUTPUT
backlight.value = True

[FoamyGuy]

I traced this back to the changes from: #10699

I made a guess that the removal of reset_all_pins(); in supervisor/port.c could be related so I checked before and after that commit and found that before the backlight does turn on, and after it does not.

I'm not actually sure if reset_all_pins() is truly related, or if I just got somewhat lucky. I haven't tried isolating the changes from this PR.

[dhalbert]

I think it's related. But we can add a backlight pin initialization to init in board.c.