PDM microphone interface

RE: PDM microphone interface

Y0g1 — Tue, 02 Mar 2021 15:34:06 GMT

sorry for being late i will check and revert u thanks for quick response.

RE: PDM microphone interface

Håkon Alseth — Wed, 24 Feb 2021 08:39:48 GMT

Hi,

As mentioned, you only need to set the config NRFX_PDM=y and set the peripheral as non-secure in spm.c, no need to add the CONFIG_COMPILER_OPT="..." with ncs v1.4.0 and newer.

[quote user="Y0g1"]i followed the link and set the values as described to spm.c now the pdm functions are working but still in dts file pdm shows disabled as below[/quote]

DT does not have any impact when using the nrfx driver directly. You are accessing the hardware peripheral directly without using the zephyr driver API.

[quote user="Y0g1"]which gives false as output. inspite all this the output i got is like this[/quote]

This function will only return true if the PDM is started, not initialized. Try checking this after you call nrfx_pdm_start().

[quote user="Y0g1"]which gives false as output. inspite all this the output i got is like this[/quote]

Can you try to let the PDM run for 1 second before stopping it? Like this:

	nrfx_pdm_start();
	bool enabled = nrfx_pdm_enable_check();
	printk(enabled ? "true/n" : "false\n");	
	k_msleep(1000);

	nrfx_pdm_stop();

Kind regards,

Håkon

RE: PDM microphone interface

Y0g1 — Tue, 23 Feb 2021 16:04:08 GMT

thanks for quick reply. i followed the link and set the values as described to spm.c now the pdm functions are working but still in dts file pdm shows disabled as below

pdm0: pdm@26000 {
				compatible = "nordic,nrf-pdm";
				reg = < 0x26000 0x1000 >;
				interrupts = < 0x26 0x1 >;
				status = "disabled";
				label = "PDM_0";
			};

i also included nrfx.h which includes nrfx_config.h which clearly showing the value NRFX_PDM_ENABLED 1.

i am using function

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

which gives false as output. inspite all this the output i got is like this

*** Booting Zephyr OS build v2.4.0-ncs1  ***
Starting PDM program!
PDM Buffer size: 3072 in 16 bit words
false
pins init!
195887104
false
200101d8 is the starting address
   0 is current value at 200101d8
The PDM will start reading NOW...
Out:    0 @ 0x200101d8
    0 @ 0x200101da
Out:    0 @ 0x200101d8
    0 @ 0x200101da
   0 is current value at 200101d8

i was trying to find out the reason that which file is over writing the pdm enable configuration. i am again including the proj.conf settings below

CONFIG_PRINTK=y
CONFIG_I2C=y
CONFIG_GPIO=y
CONFIG_NRFX_PDM=y

CONFIG_DEBUG=y 
#CONFIG_REBOOT=n

CONFIG_COMPILER_OPT="-DNRF_PDM=NRF_PDM_NS -DNRFX_PDM_ENABLED=1"

kindly check into this and help me to resolve the issue as explained before i am using a custom pcb with conf nrfx_pdm_config_t pdm_config = NRFX_PDM_DEFAULT_CONFIG(1, 0); . please guide me to resolve the issue.

RE: PDM microphone interface

Håkon Alseth — Tue, 23 Feb 2021 08:31:24 GMT

My apologies, the peripheral needs to be marked as non-secure in spm.c, as shown here:

https://devzone.nordicsemi.com/f/nordic-q-a/68472/pdm-mic-on-nrf9160dk-and-spm/281880#281880

Could you try this and see if it works better now?

Kind regards,

Håkon

RE: PDM microphone interface

Y0g1 — Sun, 21 Feb 2021 17:02:39 GMT

sir

i tried as per your guide here are my observations

1. First thing is to add the sources in zephyr/ext/hal/nordic/CMakeLists.txt:

zephyr_sources_ifdef(CONFIG_NRFX_PDM nrfx/drivers/src/nrfx_pdm.c)

i checked out my ncs v 1.4.0 the file i found at location ncs/modules/hal/nordic/CMakeLists.txt which contains the setting as discussed above

2. And you also need to add these two lines to zephyr/ext/hal/nordic/Kconfig:
config NRFX_PDM
    bool

i didnt find the second file location so can't able to verfy that.

3. Now we start on the application side. you need to append this to your prj.conf:
    CONFIG_COMPILER_OPT="-DNRF_PDM=NRF_PDM_NS -DNRFX_PDM_ENABLED=1"
    
4. Next up is selecting the NRFX_PDM in Kconfig. This is a symbol that needs to be selected by a module, so let's add one to your application.
        mainmenu "PDM test"

        config FORCE_PDM
        	bool "Test to force PDM"
        	select NRFX_PDM
            default y
        
        source "$ZEPHYR_BASE/Kconfig.zephyr"

both steps are done correctly

i also included the code below in main.c as per your saying

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);

but no luck the code output i got on terminal is like below it got stuck with any function called related to nrfx pdm.

*** Booting Zephyr OS build v2.4.0-ncs1  ***
Starting PDM program!
PDM Buffer size: 3072 in 16 bit words
pins init!

here is the code i used for tesitng found in some other tickets if that help you to guide me for the error resolution

/*  
		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 <sys/printk.h>
#include <string.h>
#include <stdlib.h>
#include <nrfx_pdm.h>
#include <stdint.h>
#include <drivers/gpio.h>



#define PDM_BUF_SIZE 3072  //length of buffer in 16 bit words

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: %4x @ 0x%x\r\n %4x @ 0x%x\r\n",
		       (uint16_t)pdm_buf[0], &pdm_buf[0],
		       (uint16_t)pdm_buf[1], &pdm_buf[1]);
	}
}

static void pdm_init(void)
{
	nrfx_pdm_config_t pdm_config = NRFX_PDM_DEFAULT_CONFIG(
		1, 0); /*configures CLK to pin 01 and Din to pin 00*/
                printk("pins init!\n");
	int err = nrfx_pdm_init(&pdm_config, nrfx_pdm_event_handler);
        printk("%u\n",err);
}

/*ISR workaround given by Nordic*/
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);  //workaround line 
	printk("Starting PDM program!\n");
	printk("PDM Buffer size: %d in 16 bit words\n", PDM_BUF_SIZE);

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

	pdm_init();
	printk("%4x is the starting address\n", &pdm_buf);
	printk("%4x is current value at %x\n", pdm_buf[0], &pdm_buf);
	printk("The PDM will start reading NOW...\n");
      /*  for (int i = 0; i < 500; i++) {
          int k = 5;
          for (volatile int j = 0; j < 50; j++) {
                k = !k;
		}
	}*/
	nrfx_pdm_start();
	for (int i = 0; i < 100; i++) {
          int k = 5;
          for (volatile int j = 0; j < 100; j++) {
                k = !k;
		}
	}
	nrfx_pdm_stop();

	printk("%4x is current value at %x\n", pdm_buf[0], &pdm_buf);
}

i am also including my proj.conf

CONFIG_PRINTK=y
CONFIG_I2C=y
CONFIG_GPIO=y
CONFIG_NRFX_PDM=y

CONFIG_DEBUG=y 
#CONFIG_REBOOT=n

CONFIG_COMPILER_OPT="-DNRF_PDM=NRF_PDM_NS -DNRFX_PDM_ENABLED=1"

please go through all the details and help me to resolve the error.

RE: PDM microphone interface

Håkon Alseth — Mon, 08 Feb 2021 11:09:49 GMT

Hi,

Do you require to use the PDM interface, or the I2S interface?

The example you're looking at uses I2S, not PDM. Do note that zephyr doesn't have a nrf-specific port for either PDM or I2S.

You can use the nrfx driver directly, but this means that you cannot rely on zephyrs sensor-implementations for the specific peripheral.

If you are interested in PDM, you can have a look at this thread:

https://devzone.nordicsemi.com/f/nordic-q-a/57896/pdm-interface

Kind regards,

Håkon