Questiona about GPIO Output (LED) example about micropython-esp32-ulp HOT 3 CLOSED

@wz2b I have now merged the fix. Thanks again for reporting it.

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You are very correct. That code is indeed incorrect. Some bad copy-pasting that happened to work(ish).

The correct way would be to set the port to output enabled once with this instruction:

WRITE_RTC_REG(RTC_GPIO_ENABLE_W1TS_REG, RTC_GPIO_ENABLE_W1TS_S + gpio, 1, 1)

and then to toggle the LED on and off with these instructions:

//on
WRITE_RTC_REG(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + gpio, 1, 1)

//off
WRITE_RTC_REG(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + gpio, 1, 0)

Alternatively one can use the RTC_GPIO_OUT_W1TS_REG and RTC_GPIO_OUT_W1TC_REG registers, but I prefer the RTC_GPIO_OUT_REG approach. I am not sure why there are two ways to do this.

I just tested this with a power profiler (nordic PPK2), which supports reading in logic signals alongside the power profile. When I connect my GPIO output to the logic port with the current (wrong) blink.py code, I can see the initial low to high transition, but the logic port never "sees" a low again (I guess with "output enable" turned off the pull-down is also disabled and the pin is left floating).

When I instead fix the code as per above, I correctly see the highs and lows of the GPIO output from via the logic port.

Thanks for picking this up. I will create a PR for this soon.

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Great, thanks explaining - I thought that was what was going on, but I'm using these examples to learn how to make a virtual SPI port in the ULP and I'm not quite used to the GPIO/RTC muxes in this thing yet.

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