Trying to drive a I2S MEMS microhpone (SPH0645LM4H) using RP2040 PIO but timing seems bad and I dont get any audio back

Question

So I want to connecte an i2s MEMS microhpone to a RP2040. I have made a PIO program that looks like this:

.wrap_target
    set pins, 1
    set pins, 0
.wrap

% c-sdk {
// this is a raw helper function for use by the user which sets up the GPIO output, and configures the SM to output on a particular pin

void blink_program_init(PIO pio, uint sm, uint offset, uint pin) {
   pio_gpio_init(pio, pin);
   pio_sm_set_consecutive_pindirs(pio, sm, pin, 1, true);
   pio_sm_config c = blink_program_get_default_config(offset);
   float divider = 20;
   sm_config_set_clkdiv(&c, divider);
   sm_config_set_set_pins(&c, pin, 1);
   pio_sm_init(pio, sm, offset, &c);
}
%}

So very simple. I also adjusted the clock speed so that one cycle would be 333 nS

My problem is that

1. It seem like the timing is wrong quite frequently. Why could this be?

2. I dont get any audio data back from the MEMS microphone, There are something happening but I do not think it should look like this

Here is my breadboard, note that the colors of the cables corresponds to the logic analyser channel colors

These are the cable colors:

Yellow -> I2S, Clock

Green -> LRCL / WS / Frame Select

Blue -> DATA OUT

Any idea where I can start troubleshooting?

Answer 1

1. With the logic analyzer sampling at 12 Msps, each 4 MHz clock period is only 3 samples. It should always look like 33% or 66% duty wave, and the sampling is not synchronous. Expect to see what you are already seeing there, or maybe the clock is slower that 4 MHz if it samples mostly 2 high and 2 low samples per period.

2. The LRCLK/WS signal is not according to I2S norms or even what the mic requires. It must be a square wave with certain amount of clock cycles high and low.