Using PDM Mic on nRF9160DK

[octvargas]

I was wondering if there were any good examples of how to get a PDM device (in this case a microphone) working on the nRF9160DK. I've read parts of the datasheet and I've been able to find the nrfx_pdm driver in the SDK but am unaware what pins to use to get it to read data and how to use the easy-dma feature.

Any pointers in the right direction are appreciated. Thank you

[Einar Thorsrud]

It could be empty. There is a configuration hierarchy, so unless you need to change some of the default configurations (such as in zephyr\boards\arm\nrf9160_pca10090\nrf9160_pca10090ns_defconfig), you don't need anything.

[octvargas]

yeah, that's what I was afraid of. Thanks, I'll try and track down the problem w/ warnings like you suggested.

Thank you

[octvargas]

okay, so I tried adding 

#ifndef NRFX_PDM_ENABLED
#warning NRFX_PDM_ENABLED is undefined
#else
#if !NRFX_PDM_ENABLED
#warning NRFX_PDM_ENABLED is defined but set to 0
#endif
#endif

to nrfx_pdm_ns.h, nrf_pdm_ns.h both to no results

however, once I added it to nrfx.h I get this warning

so I then proceeded to add this to both nrfx_glue.h and nrfx_glue.c

#ifndef NRFX_PDM_ENABLED
#define NRFX_PDM_ENABLED 1
#endif

But even after adding that, I still get the same exact errors and the same exact warnings

[octvargas]

So I changed up my code to test if the PDM was enabled using 

nrfx_pdm_enable_check()

shockingly it did not give me an undefined reference error, however when I tried to run the code it did give me this error

here is my edited code

Fullscreen 5557.main.txt Download

/*  
		C Program to run a pulse density modulation (PDM) Microphone on the nRF9160 Dev Kit using the Nordic SDK
*/

#include <nrf9160.h>
#include <zephyr.h>
#include <misc/printk.h>
#include <string.h>
#include <stdlib.h>
#include <nrfx_pdm_ns.h>
#include <nrfx_pdm.h>

#include <gpio.h>


#define PDM_BUF_ADDRESS 0x20000000 // buffer address in RAM
#define PDM_BUF_SIZE 256 //size in 32 bit words --> 1KB

int16_t pdm_buf[PDM_BUF_SIZE];

/*
void nrfx_pdm_event_handler(nrfx_pdm_evt_t const *const p_evt)
{
	if (p_evt->buffer_requested) {
		//nrfx_pdm_buffer_set(pdm_buf, PDM_BUF_SIZE);
	}
	if (p_evt->buffer_released != 0) {
		printk("Out: %.2x %2x\r\n", (uint16_t)pdm_buf[0],
		       (uint16_t)pdm_buf[1]);
	}
}
*/ 

//static void pdm_init(void)
//{
//	nrfx_pdm_config_t pdm_config = NRFX_PDM_DEFAULT_CONFIG(10, 11); /*configures CLK to pin 10 and Din to pin 11*/
//	//nrfx_pdm_init(&pdm_config, nrfx_pdm_event_handler);
//}

void main(void)
{
	printk("Starting PDM program!\n");
	//printk("PDM Buffer size: %d\n", (PDM_BUF_SIZE * 4));
	//printk("PDM Starting Address: %x\n", PDM_BUF_ADDRESS);

        bool enabled = nrfx_pdm_enable_check();
        printk(enabled ? "true/n" : "false\n");

	//pdm_init();
}

I am very confused

[Einar Thorsrud]

Hi,

This seems to be because of the Secure Partition Manager (SPM) is not configured to make the PDM peripheral non-secure. You can fix it by adding PDM to the periph_cfg list in spm.c. You can add the following line in the list:

PERIPH("NRF_PDM", NRF_PDM_S, 1),