RE: freedom pdm clock set

Sigurd — Mon, 12 Jun 2017 13:31:39 GMT

Hi,

Only the values listed in the PS have been fully and thoroughly tested. If you are using values that are not listed in the PS, we cannot guarantee that they will work and it will be on your own risk.

With that said, you should be able to set the clock to a different frequency, e.g. PDM_CLK = 32 MHz / 26 = 1.231 MHz -> use NRF_PDM->PDMCLKCTRL = 0x09800000; before you start the PDM.

But, you will not be able to fine adjust the clock frequency, since the PDM clock generator does integer division based on the HFCLK. You can therefore not set the PDM clock 100% freely. Some additional values are listed for the nRF52840, see this link.