Could not set I2S master clock line with mck keyword

[saraverbeecke]

I'm trying to initialize a I2S object as described in the docs: https://docs.micropython.org/en/latest/library/machine.I2S.html but the keyword mck seems not to work.
Any ideas?

I'm using an Generic ESP32 board with SGTL5000 Codec:

from machine import Pin, I2S
sck_pin = Pin(15)
ws_pin = Pin(16)
sd_pin = Pin(17)
mck_pin = Pin(18)
audio_in = I2S(0, sck=sck_pin, ws=ws_pin, sd=sd_pin, mck=mck_pin, mode=I2S.RX, bits=16, format=I2S.MONO, rate=22050, ibuf=20000)

[jimmo]

The mck argument is only supported on the m.iMX port. We should clarify that in the documentation.

[karfas]

Which micropython version do you use ?

The mck keyword is currently not supported by micropython.

Even when #8110 solves an initialization bug with the mck configuration, I can't see anywhere in the ESP32 port that mck=Pin gets evaluated as a parameter.

I'm pretty sure this is a bug.

[robert-hh]

As @jimmo said, a mclk signal is not generated by the ESP32 I2S hardware. But you can create a mclk signal using PWM.
See also https://forum.micropython.org/viewtopic.php?f=2&t=12405&p=67381&hilit=I2S+ESP32#p67381

[karfas]

No. @jimmo said, "it is not supported".
While I have no idea which hardware variant of the ESP32 can or can't generate mclk, I'm pretty sure it's in the ESP-IDF configurable for a reason.
See e.g. https://docs.espressif.com/projects/esp-idf/en/v4.4.2/esp32/api-reference/peripherals/i2s.html

[robert-hh]

Ok. So it seems to be not supported by the MP driver. Still you can generate the mclk signal for the SGTL5000 codec by a PWM, channel. Maybe Mike will find the time to update the ESP32 I2S module.

[saraverbeecke]

@karfas I'm using the latest build 1.19-1.

Thanks for the answers!

[miketeachman]

It's on my todo list to add Master clock support to the other ports, but admittedly it's not high on my agenda, mainly because the most popular I2S devices do not need a Master clock signal. e.g. the devices listed here and here

One challenge for the ESP32 is the varying level of Master clock support for the different ESP-IDF versions that MicroPython supports. For example, MicroPython supports ESP-IDF versions v4.0.2, v4.1.1, v4.2.2, v4.3.2 and v4.4. Of these, only v4.4 supports a Master clock output. So, that would mean adding conditional compilation macros into the I2S code to detect what version of ESP-IDF is being used, to turn on/off the Master clock feature. These macros in turn drive regression testing to make sure the I2S feature still builds and works correctly when someone uses say ESP-IDF v4.0.2. As a volunteer contributor with a busy life, this work has somewhat limited appeal, especially when the Master clock feature can be replicated with machine.PWM.