I never arrived at a satisfactory solution for the S3. My next idea would've involved an intermediary between the S3's dual I2S and the codec to translate it to one single data line.

I'm now using the P4 with TDM8 32-bit on a single data wire.


Thanks for the quick response! Too bad, I was ...

One way to do it (might be the same as @thefury) is:

Configure one of the I2S as slave then share the clock signal.

The GPIO trick can be referred to from components/esp_driver_i2s/test_apps/i2s/main/test_i2s.c:
i2s_test_io_config . After I2S finishes initializing GPIO, use esp_rom_gpio ...