pdm interfcae with nrf5340 and live data transfer

RE: pdm interfcae with nrf5340 and live data transfer

Karl Ylvisaker — Wed, 13 Dec 2023 20:23:31 GMT

Hello,

Let us continue this discussion in your other open ticket on the matter so as to not duplicate the questions and information.

Best regards,
Karl

RE: pdm interfcae with nrf5340 and live data transfer

manikandan — Wed, 13 Dec 2023 05:05:41 GMT

hi Karl Ylvisaker any inputs?

RE: pdm interfcae with nrf5340 and live data transfer

manikandan — Tue, 12 Dec 2023 05:26:38 GMT

Hi, thanks for your reply.

Our requirement is a 512 kHz clock with a sampling frequency of 4 kHz and a decimination ratio of 128.

1) Is it possible to set the NRF_PDM0->PDMCLKCTRL register to 512 KHZ? If yes, what would be the NRF_PDM0->PDMCLKCTRL register value? And how are we calculating it?

2)I have seen this document: https://infocenter.nordicsemi.com/index.jsp?topic=%2Fps_nrf5340%2Fpdm.html Only ratio 40 and 80 were used. Is this the only possible decimination ratio that can be used? If not, how can I set the ratio in this register, NRF_PDM0->RATIO? ie:128

3)I have attached distorted audio filedevzone.nordicsemi.com/.../audio.wav kindly check.

Regards,

Manikandan V

RE: pdm interfcae with nrf5340 and live data transfer

Karl Ylvisaker — Mon, 11 Dec 2023 15:04:30 GMT

Hello Manilkandan V,

[quote user=""]

How is the PDM clock genrated in the below calculation?

[/quote]

In that example it is using the 32 MHz crystal for the clock source.

[quote user=""]     // set 1280kHz frequency
    NRF_PDM0->PDMCLKCTRL = 0x0A000000;
    // set factor of 80 to get 16kHz sampling frequency
   NRF_PDM0->RATIO = 1[/quote]

I notice that you are writing to the registers directly here, is this a requirement for your application or could it be an alternative to use the nrfx pdm driver instead? I would recommend using the driver over the register manipulation approach.

[quote user=""]currently mic is working at 1280khz frequency but audio seems to distorted?[/quote]

Could you describe this distortion - is it a constant noise, like a filter or offset, an intermitting distortion, or audiable artifacts like clicks and pops?

Best regards,
Karl

RE: pdm interfcae with nrf5340 and live data transfer

manikandan — Mon, 11 Dec 2023 06:10:51 GMT

any inputs?