Got time to make more tests, this time on the S3, got pretty similar results. Unfortunately, I couldn't get it to reliably receive a 64 byte frame attached to the wakeup character. For about 20 bytes, I could get it to reliably receive by using the RC fast clock for both UART and RTC, and low baud ...

@ves011: thanks a lot for the info. Were you receiving data during light sleep? If you were using the UART only for the debug trace, and did not receive data, that's a different use case.

I have been doing some more tests with the C3 (that I would like to confirm work the same on the S3, but couldn ...

But is it possible at all? How? The links provided are quite basic and do not help for my questions.

I am using an ESP32-S3 with two UART connected peripherals.

To reduce power drain, I am using DFS and I want to implement auto light sleep. But when the chip enters light sleep, it looks like the UART stops working (either power is removed, clock is removed or both, I don't know). But I need the ...

After HOURS of digging, I found the problem.

It looks like by default, pins are configured with IO_MUX_SLP_SEL = 1, because calling gpio_sleep_sel_dis() on a pin, caused it to not drop its value during light sleep.

I wonder why this is the default, doesn't make too much sense to me, but at least I ...

I am a bit confused with the behavior of GPIO outputs with light sleep. I know that deep sleep deactivates GPIOs unless you configure them to maintain the value (e.g. with rtc_gpio_hold_en()). But I was not expecting light-sleep to also deactivate GPIO outputs.

My code calls esp_pm_configure() with ...

Yes, you can choose "Run FreeRTOS on first core only" option in menuconfig, Component config > FreeRTOS menu and build the application again. That will disable 2nd CPU and all the tasks will run on the 1st.


Does this really disable the second core? Or will it be active but idling? I have an app ...

A bit late but today I was wondering the same. It looks like it is possible but not trivial, it involves creating a custom DCE, here is a patch that incorporates it to the console example: https://github.com/espressif/esp-protoc ... 660991194c

The impedance has not yet been added to the datasheet. Is there any info on this?

In an interesting turn of events, this seems to be supported by latest esp-idf (5.1), including documentation and an usage example !

Unfortunately only ESP32-S3 and ESP32-C3 support this feature right now, so for the good old ESP32, we still have no way to do it. I have opened a GitHub issue to see ...