board pins initialization?

[stanelie]

Hello.
Not sure if this is a bug report or a feature request, but I was wondering if there is a way to prevent IO pins from changing state randomly while the device boots?

I use these ESP32-S3-Zero boards to build wireless light sources, I use 4 pins as PWM outputs to drive some LED drivers. While the ESP32 boots circuitpython, before my program runs, the pins go through a cicle of full on - full off, which makes my LEDs go full on while the ESP boots. In my case, in a professional theater context, this is undesired behavior. Also, when I experience low power conditions, when the battery is drained, the ESP32 reboots constantly, which makes the LED blink on each cycle, which is even worse. Is there a way to avoid this (without having to add component to physically enable the outputs only when the device is properly booted)?

Thanks!

[dhalbert]

The pins may be going from unconnected to pulled up. The default reset state for a pin is to enable the internal pullup, which is roughly 50 kohms: this minimizes power draw, believe it or not. We used to reset the pins to float, but changed it to the standard reset state several years ago.

I think the reliable thing to do here is to put a stronger external pull-down resistor on these pins, like 10k. That will ensure that pin fluctuations during restart don't affect your outputs.

[stanelie]

Oh!
That's a great idea, and it won't need too many extra components. I like this!

Thanks!!

[dhalbert]

Let us know if you are still seeing glitches after that!

[stanelie]

Very nice! It works perfectly!

Thanks again!!