NeoPixels can't be disabled

[dhalbert]

@FoamyGuy and https://forums.adafruit.com/viewtopic.php?f=60&t=186080 report NeoPixel disabling no (no longer/) works.

Example:

magtag.peripherals.neopixel_disable = False
magtag.peripherals.neopixels.fill((100, 0, 0))
time.sleep(2)
print("disabling neopixels")
magtag.peripherals.neopixel_disable = True
magtag.peripherals.neopixels.fill((0, 0, 100))

Pixels still turn blue.

[FoamyGuy]

A bit more troubleshooting reveals that when the library attempts to initialize the DigitalInOut for the NEOPIXEL_POWER pin the system believes that NEOPIXEL_POWER_INVERTED is already in use. The code from here:

Adafruit_CircuitPython_MagTag/adafruit_magtag/peripherals.py

Lines 47 to 52 in e1e6a63

	try:
	self._neopixel_disable = DigitalInOut(board.NEOPIXEL_POWER)
	self._neopixel_disable.direction = Direction.OUTPUT
	self._neopixel_disable.value = False
	except ValueError:
	self._neopixel_disable = None

Is raising and catching the error. I added raise e into that except block to verify and I can see the traceback:

Traceback (most recent call last):
  File "code.py", line 109, in <module>
  File "/lib/adafruit_magtag/magtag.py", line 102, in __init__
  File "/lib/adafruit_magtag/peripherals.py", line 54, in __init__
  File "/lib/adafruit_magtag/peripherals.py", line 49, in __init__
ValueError: NEOPIXEL_POWER_INVERTED in use

[FoamyGuy]

I have also found that bypassing the library and directly handling the NEOPIXEL and NEOPIXEL_POWER pins does work as expected. With the following code we see the red light and the neopixels are turned off so we never see the blue light:

import time
import board
import neopixel
from digitalio import DigitalInOut, Direction

neopixel_disable = DigitalInOut(board.NEOPIXEL_POWER)
neopixel_disable.direction = Direction.OUTPUT
neopixel_disable.value = False

pixel_pin = board.NEOPIXEL

num_pixels = 4

ORDER = neopixel.GRB

pixels = neopixel.NeoPixel(
    pixel_pin, num_pixels, brightness=0.1, auto_write=False, pixel_order=ORDER
)

pixels.fill((255, 0, 0))
pixels.show()
time.sleep(1)
neopixel_disable.value = True


pixels.fill((0, 0, 255))
pixels.show()
time.sleep(1)

[FoamyGuy]

I think I understand the root of this issue. the neopixel library is initializing NEOPIXEL_POWER itself now here:

https://github.com/adafruit/Adafruit_CircuitPython_NeoPixel/blob/9ca3bf00c6a2dd1de2d315a3b952a381d720aa7d/neopixel.py#L129-L143

This means it's already in use by the time the MagTag library tries to initialize it.

With my other direct pin example above I initialized the power pin first so it was in use when neopixel tried to initialize it and it silently catches that error and moves on.