Using PDM microphone on nrf5340

RE: Using PDM microphone on nrf5340

BrianW — Wed, 02 Oct 2024 09:54:29 GMT

Yup, that works thanks and I get audio data...Now to work on the audio processing so it actually sounds like me..

RE: Using PDM microphone on nrf5340

Edvin — Wed, 02 Oct 2024 08:12:16 GMT

Yes. I think that should be pointing to the nrfx_pdm_irq_handler() in nrfx_pdm.c.

Best regards,

Edvin

RE: Using PDM microphone on nrf5340

BrianW — Tue, 01 Oct 2024 07:06:24 GMT

Ok... I thought that as I was using the nrfx_pdm driver, it took care of the low level register poking...

So this was what nrfx_pdm_init() did, as I pass my callback to that:

errcode = nrfx_pdm_init(&config1, _drv_pdm_handler);

rather than me doing it. The irq handler must be in the driver (which then calls my handler when it needs a new buffer etc)

I can add

IRQ_CONNECT(DT_IRQN(PDM_NL), IRQ_PRIO_LOWEST, _nrfx_XXX_handler, 0, 0);

but what would be the handler function in the pdm driver?

RE: Using PDM microphone on nrf5340

Edvin — Mon, 30 Sep 2024 22:22:38 GMT

Hello,

I am sorry for the late reply!

It looks like you are not forwarding the interrupt to your driver.

Please open VS Code in your NCS directory, and search for "IRQ_CONNECT(NRFX_IRQ_NUMBER_GET(", and you will see a lot of examples that are doing this. Unfortunately, not for the PDM, but a lot of other peripherals, such as UART:

#if defined(__ZEPHYR__)
    IRQ_CONNECT(NRFX_IRQ_NUMBER_GET(NRF_UARTE_INST_GET(UARTE_INST_IDX)), IRQ_PRIO_LOWEST,
                NRFX_UARTE_INST_HANDLER_GET(UARTE_INST_IDX), 0, 0);
#endif

The error that you are seeing is that you are setting up your PDM, and enabling interrupts, and then an interrupt occurs, but the application doesn't know where to send it.

I am not really sure whether the PDM has these macros t point to it's base, but if you are building for the nRF5340, the NRF_PDM0_S_BASE is found in nrf5340_application.h file, and is either 0x50026000, or 0x40026000 if you are building for nrf5340dk_nrf5340_cpuapp_ns.

Then make it point to your _drv_pdm_handler().

Best regards,

Edvin