Hi Matrix Community,

I’ve been playing with matrix voice and recorded tones at different frequencies. With original FPGA code on matrix voice, I get around 160Hz frequency offset. I’ve looked at the FPGA code to figure out this problem. Here is my finding.

In “matrix-voice-fpga/voice_core/system.v” there is a parameter “PDM_FREQ_HZ” which is equal 3_000_000. When I change this value, the frequency offset changes.

## FPGA code:

parameter PDM_FREQ_HZ = 3_000_000 , /* this frequency must be multiple of 16000, 22000, 44000, 48000 Hz */**

My questions:

- Should this parameter be a multiple of the values above as it mentioned? If yes, why it’s not in the code?
- Is 22000 and 44000 correct? If this is related to audio rate, should we consider 22050 and 44100?

I appreciate if anyone can help on this.

Thanks.