Single NeoPixel should be near White but is very Yellow Moderators: adafruit_support_bill, adafruit

[westfw]

Just pointing out that the CircuitPython code and the Arduino code for b;asting out the bitstream are substantially different.

I checked and instrumented the Arduino code; there isn't any color correction in there - when I type "9 9 10" in my test sketch, that's what the guts of show actually try to send...

[westfw]

Aha! I think I've got it.

You want the supply voltage to the pixel.

This was a clue!

On QT Py, the neopixel is powered by an output pin of the SAMD, but the SAMD output pin is never configured for high output drive, so the neopixel ends up underpowered.

Try adding this line your your setup() code:

Code: Select all | TOGGLE FULL SIZE

  PORT->Group[0].PINCFG[15].bit.DRVSTR = 1;  // turn up neopixel power

[adafruit2]

thanks @westfw - we can get this fixed up in future releases to make sure DRVSTR is higher
that said....we *are* underdriving the neopixel voltage. so your best bet is to tweak down the red if you want a pure white - we aren't using this LED as a color-true illumination, its more of a multi-color indicator that doesnt use 3 PWM channels :)

[swooby]

Aha! I think I've got it.

You want the supply voltage to the pixel.

This was a clue!

On QT Py, the neopixel is powered by an output pin of the SAMD, but the SAMD output pin is never configured for high output drive, so the neopixel ends up underpowered.

Try adding this line your your setup() code:

Code: Select all | TOGGLE FULL SIZE

  PORT->Group[0].PINCFG[15].bit.DRVSTR = 1;  // turn up neopixel power

That fixes it! You rock!

I would expect that to either:
1) be default Arduino board library's boot behavior for the 16th pin (0 based pin #15).
-or-
2) be clearly documented that it is needed in the Arduino guides (https://learn.adafruit.com/adafruit-qt- ... rduino-ide).

Is...

Code: Select all | TOGGLE FULL SIZE

PORT->Group[0].PINCFG[15].bit.DRVSTR = 1;

...the best way to write that code, or is there a better API way to set that value?

I also noticed that there is no capacitor on the neopixel and was wondering if that could cause an issue...unless the 16th pin has any sort of internal capacitor.

[swooby]

thanks @westfw - we can get this fixed up in future releases to make sure DRVSTR is higher
that said....we *are* underdriving the neopixel voltage. so your best bet is to tweak down the red if you want a pure white - we aren't using this LED as a color-true illumination, its more of a multi-color indicator that doesnt use 3 PWM channels :)

Understood; Feedback from a "I still consider myself a noob" is that I look at that built-in neopixel as a stepping stone to get more familiar with how to control a single pixel before graduating to controlling to larger strips or matrices.
If there is something unique about controlling that pixel that does not scale to the standard way a neopixel is controlled or driven, then that would be nice to mention and educate in a guide.

[adafruit2]

we're gonna fix it, so just keep your board updated when the ide tells you to later this week :)

[westfw]

Bug report: https://github.com/adafruit/ArduinoCore-samd/issues/311
and patch: https://github.com/adafruit/ArduinoCore-samd/pull/312

Frequently, it can take "a while" to distinguish between actual bugs, and misunderstandings of expected behavior.
Swooby's post showed up shortly after I had noticed color problems of my own with a QTPy. Originally I had shrugged them off, but this caused be to take a more careful look!

[swooby]

Thanks everyone, and Happy Holidays and Merry Christmas!

[swooby]

w00t!
https://github.com/adafruit/ArduinoCore-samd/pull/313
Almost there.

Again, thanks all!