esp32: Add I2S peripheral support.

[aykevl]

Implementation of hardware I2S for the ESP32.

This appears to be the first I2S implementation for MicroPython. I've followed the proposed I2S machine API mostly, but did not follow it exactly. This is the current API / example code:

import machine
i2s = machine.I2S([0,] bclk=4, ws=15, data_out=2, data_in=22, [samplerate=48000,] [bitdepth=16])
buffer = ... # generate sine wave or something
while True:
    i2s.write(buffer)

# also implemented
i2s.deinit()
i2s.init(...) # throws an error if initialized already

Not yet implemented, mostly due to lacking hardware:

• communication format, e.g. MSB/LSB.
• clock: the ESP32 has an APLL clock, but I'm not sure what it's purpose is
• callbacks (for now, i2s.write() blocks if the buffer is full)
• reading from the I2S bus
• not setting the data_in pin (not sure if this is possible)
• change parameters
• stop/start (without deinit) - by default it keeps looping existing data if the buffer isn't filled fast enough
• internal ADC

Which of these (if any) should be implemented before it can be merged?

Documentation: https://esp-idf.readthedocs.io/en/latest/api-reference/peripherals/i2s.html

[aykevl]

I've noticed this must be configurable somehow. For example, for stereo 48kHz 20ms packets (Opus) it needs to be at least 120.

[AidanTek]

Hello - I'm very interested in helping to make this happen, I see your pull request is from some time ago, I'm new to firmware but have experience with audio and embedded audio design. I have a variety of ESP32 versions and also audio codecs for both input and output (PCM5102A and PCM1808) more than happy to help where I can

[nevercast]

A newer PR for the same is here: #4471

[dpgeorge]

I2S was implemented in 8a5bfe4