Hello,
We used our old rev board to prototype some new features including a new PDM digital microphone. It worked great using the nrfx_pdm module. When we spun a new rev of our board to use this, we used different pins, and have had trouble getting PDM to work at all on the new board.
We had the prototype working, connecting PDM CLK to P0.28 and DATA on P0.31. On the new board, we have CLK on P1.12 and DATA on P1.03. I've confirmed that with the same code, CLK is not clocking, but is fixed at GND while the PDM driver is active. I've tried a couple configurations to troubleshoot. If I remove the mic from the board, I can switch the CLK and DATA and still don't get any output on the CLK line (i.e. no clock signal on P1.12 or P1.03). If I set the CLK pin to 0.31, the clock signal is clearly discernible.
Is there any limitation on what pins can be used for PDM? I haven't found any such notes in the documentation or errata. I did discover a fact we missed during our board design, that both the pins used on this rev of the board and in prototyping are noted as "low frequency only". So we may have to change this for production, but since the P0 pins worked in the prototype we are stumped as to why the P1 pins won't work for us on this board, and this is holding up our development efforts.
Please let me know if you can shed any light on this question
