PDM interface

[borg]

We have a product with a microphone with PDM output that uses the nrf9160.

The nrf9160 does have a PDM hardware unit that looks well suited to read it out.

But currently there is no nrf9160 support for PDM in zephyr and there are also no examples for PDM available. Is that correct?

Is there any chance that we can get a simple PDM example that we can use as a starting point?

[Håkon Alseth]

Hi,

 

If you add this to your prj.conf:

CONFIG_NRFX_PDM=y

 

Then you should be able to access the nrfx driver directly in your application, by including "#include <nrfx_pdm.h>" in your .c file, and interface it.

The "old" way of doing this, prior to tag v1.2.0, is described here:

https://devzone.nordicsemi.com/f/nordic-q-a/50656/using-pdm-mic-on-nrf9160dk/204715#204715

If you are using a fairly recent ncs, you should need to follow the very last step only, where you direct the interrupt in your main.c file:

ISR_DIRECT_DECLARE(pdm_isr_handler)
{
	nrfx_pdm_irq_handler();
	ISR_DIRECT_PM(); /* PM done after servicing interrupt for best latency
			  */

	return 1; /* We should check if scheduling decision should be made */
}

void main(void)
{
	IRQ_DIRECT_CONNECT(PDM_IRQn, 0,
			   pdm_isr_handler, 0);
	/* Rest of main */

 

Note: when compiling for non-secure, you need to set the peripheral as non-secure directly, as shown here: https://devzone.nordicsemi.com/f/nordic-q-a/68472/pdm-mic-on-nrf9160dk-and-spm/281880#281880

 

Kind regards,

Håkon

[borg]

Thanks a lot! I will try this and report back.