ESP32/ESP32S3 RMT

[sam131208]

Is your feature request related to a problem? Please describe.
In general, when applying an LED strip, we like to use SPI to transmit the signal to it.Sometimes, however, the transmitted signal is interrupted by other interruptions. In addition, it also occupies additional SPI ports.

Describe the solution you'd like
RMT does a better job of driving a small number of LED strips, it is not interrupted by other interrupts, and it does not need to occupy DMA.

Describe alternatives you've considered
There is no better way to drive the LED strip than the RMT, when the number of led strips is less than 16, the FIFO using RMT can drive the led strip perfectly.

[shenyi97]

I just start to work on the RMT driver on ESP32S3. Do you have any advices about the design of RMT api? Is it a good idea to keep it consistant with esp-idf api?

[patelvijay12007]

Any progress on this driver? We need it to drive neopixel LEDs.

[MeisterBob]

@shenyi97 are you still working in a RMT driver? Is there anything I can help you with or anything I can use for further development in case you aren't working on this anymore?

[joelguittet]

@sam131208 @shenyi97 @patelvijay12007 @MeisterBob hello! anyone working on this support? I will appreciate to help to have this support :-)

@sylvioalves maybe you can also help on the status from Espressif? Is support of RMT something you are working on?
I see there are missing parts in hal_espressif (only a a few rmt hal functions in rmt_hal.c), and probably a custom driver in zephyr repository? The question of @shenyi97 is interesting: what is the approach you would adopt to add a driver in zephyr, particularly about APIs? Trying to match esp-idf driver APIs or not?

[joelguittet]

@sylvioalves @sam131208 @shenyi97 @patelvijay12007 @MeisterBob I have work a bit using the led strip example https://github.com/espressif/esp-idf/tree/v5.1.6/examples/peripherals/rmt/led_strip to validate the possibility to port the RMT support on Zephyr.

I have draft this using an ESP32, and I'm able to produce the expected waveform based on this example. I need to cleanup before proposing something. I have not integrated support for DMA and PM.

So the RMT should then be available on ESP32, ESP32H2, ESP32C3, ESP32C6 and ESP32S2. Only ESP32S3 is using DMA.

I will post here and if some of you would like to test/provide feedbacks/fixes, they will be very welcome!!

[sylvioalves]

@joelguittet, hey! That sounds great! Looking forward to it.

[sylvioalves]

I think this driver should be add in zephyr/drivers/misc/espressif_rmt. Have you thought about it?

[joelguittet]

I think this driver should be add in zephyr/drivers/misc/espressif_rmt. Have you thought about it?

Yes why not!

[joelguittet]

@sylvioalves you are assigned to #101448 and zephyrproject-rtos/hal_espressif#510, please do not hesitate to comment, I'm very happy to contribute with this PR :-)

For the 2 errors mentioned, if you have an idea for the ESP32S2 I'm very interested.
For the ESP32S3 and DMA support, is it something that is mandatory ? Is it possible to just not use DMA with the RMT on ESP32S3? By the way, if you have a guide to convert from gdma to zephyr DMA APIs, I'm also interested. I have not spent much time on it but this should come.

[fabiobaltieri]

In general, when applying an LED strip, we like to use SPI to transmit the signal to it.Sometimes, however, the transmitted signal is interrupted by other interruptions.

You need to run the SPI port with DMA enabled, there's few samples in samples/drivers/led/led_strip/boards, I2S also works (also with dma).