I2S example for RPi Zero W.
This code generates I2S signal using RPi's PCM I/O hardware.
The signal is 8KHz sampled 16bit stereo.
Connect I2S device (DAC for example) to monitor the signal.
(WARNING! the sound is very LOUD. Please turn the volume down.)
BCLK: GPIO18, FS: GPIO19, DOUT: GPIO21