What do I misunderstand about rgbled()?

[Gijs]

So if I understand this correctly, the loop

pycom.heartbeat(False)
While True:
   rgbled(green)

does not show a green color on the led because we call it too fast, leaving no time to actually change the led as we queue another task to change the led color right after the first one, squashing the first one? That would make sense.

Thanks for the thorough explanation! I would not have expected that and figured the method to be blocking until the LED color actually changed. Do you think this is a bug, or a feature?

Gijs

[robert-hh]

@Gijs Not really. It is not that a follow up call to rgbled() squashes the previous one. It is the opposite. If the follwow-up call is too early, it will be ignored. And in the example it was the rgbled(white) which came too soon, only ~50 µs after the previous one.
The messages themselves had proper structure, only the time between them was too short.

Adding more time (here 144 µs) made it work.

I made a PR ensuring at least 280 µs, because that's what I found in the datasheet of the WS2812B-V4 (opposed to 50µs in the WS2812B datasheet).

[robert-hh]

@Gijs said in What do I misunderstand about rgbled()?:

I would not have expected that and figured the method to be blocking until the LED color actually changed. Do you think this is a bug, or a feature?

Using the RMT is definitly a feature. The code actually waits until a previous transmission is finished. And that's the heart of my PR. I just insert another wait pulse cycle pair to the RMT chain, which causes a sufficient delay. I was not able to find the place causing the 50µs delay which is initially there.

[Paul Holthuizen]

@robert-hh

For my benefit: what's the RMT?

[robert-hh]

@Paul-Holthuizen That is the Remote Controller Unit of the ESP32. Intended to send and receive messages for remote controllers. But it is also fine for creating and timing bit patterns with high precision. See https://docs.pycom.io/firmwareapi/pycom/machine/rmt/#app

[Paul Holthuizen]

@robert-hh

And precise enough to create the timing signals for a WS2812! I remember writing a piece of C-code for a PIC microcontroller controlling a whole string of these leds and wrestling with that for a bit.

Thanks for your support. I was getting a little bit frustrated with the lopy on my bench but am starting to realize now that the difficult bit here is not in the networking but in the way a high-level language like Python interfaces with low level hardware. Just more stuff to learn :-)