Using PDM Mic on nRF9160DK

RE: Using PDM Mic on nRF9160DK

FinKM — Wed, 26 Apr 2023 12:09:44 GMT

Håkon Alseth Einar Thorsrud I'm looking at getting a PDM mic working with an nRF9160, but on NCS 2.3/TFM 1.6/Zephyr 3.2.99.

Is there an up-to-date reference on how to do this, and furthermore is it possible to use the Zephyr DMIC library on-top of the Nrfx PDM driver?

RE: Using PDM Mic on nRF9160DK

octvargas — Mon, 19 Aug 2019 13:36:51 GMT

Compiles properly now, thank you!

RE: Using PDM Mic on nRF9160DK

Håkon Alseth — Mon, 19 Aug 2019 11:01:05 GMT

Hi,

This isn't straight-forward due to the PDM not being natively supported.

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)

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

config NRFX_PDM
    bool

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"

This will enable the module, and define NRF_PDM to NRF_PDM_NS.

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.

Create the file "Kconfig" in nrf/samples/nrf9160/my_sample/ and paste into the file:

mainmenu "PDM test"

config FORCE_PDM
	bool "Test to force PDM"
	select NRFX_PDM
    default y

source "$ZEPHYR_BASE/Kconfig.zephyr"

You can name the config what-ever you'd like, in this case it is "FORCE_PDM", and it's default y (so no need to manually add it to your prj.conf in this case).

Could you try these steps and see if it compiles properly now?

Sorry for the comprehensive workaround and the inconvenience.

*edit* in order to use the non-blocking (ie: the handler function), you have to add this to your main to forward the interrupt vector:

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 */

Kind regards,

Håkon

RE: Using PDM Mic on nRF9160DK

octvargas — Fri, 16 Aug 2019 13:30:14 GMT

Hi Einar,

so I added these lines to zephyr\ext\hal\nordic\CMakeLists.txt

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

I then re-built the project and tried to build the solution, and still got the same undefined reference errors. Did I add the correct lines, or was there something I missed?

Thanks

RE: Using PDM Mic on nRF9160DK

octvargas — Fri, 16 Aug 2019 13:19:31 GMT

that makes sense, I'll check on that. One thing I find odd though, how am I able to use the nrfx_pdm_enable_check() function if it's part of the same header file?

RE: Using PDM Mic on nRF9160DK

Einar Thorsrud — Fri, 16 Aug 2019 11:28:23 GMT

Hi,

I just thought of one obvious thing. Since PDM is not supported yet, nrfx_pdm.c is not even included in zephyr\ext\hal\nordic\CMakeLists.txt, so it is never compiled. So it is no wonder you get the undefined reference. You need to add it to the list of tiles in zephyr\ext\hal\nordic\CMakeLists.txt.

RE: Using PDM Mic on nRF9160DK

octvargas — Thu, 15 Aug 2019 13:23:27 GMT

So, uh, I forgot to uncomment out my buffer_set function, they're both still undefined reference.

RE: Using PDM Mic on nRF9160DK

octvargas — Thu, 15 Aug 2019 13:21:08 GMT

Awesome, so I tried your fix, and am no longer getting a bus fault error. Also for some reason my undefined reference to buffer set is gone, but my undefined nrfx_pdm_init is still there

RE: Using PDM Mic on nRF9160DK

octvargas — Thu, 15 Aug 2019 13:06:06 GMT

Hi Einar,

Would that work to make it non-secure? Most the other ones I can see have an NS at the end whereas this has PDM_S at the end. Is that correct?

RE: Using PDM Mic on nRF9160DK

Einar Thorsrud — Thu, 15 Aug 2019 07:12:39 GMT

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),

RE: Using PDM Mic on nRF9160DK

octvargas — Wed, 14 Aug 2019 17:59:01 GMT

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

devzone.nordicsemi.com/.../5557.main.txt

I am very confused

RE: Using PDM Mic on nRF9160DK

octvargas — Wed, 14 Aug 2019 15:17:09 GMT

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

RE: Using PDM Mic on nRF9160DK

octvargas — Wed, 14 Aug 2019 13:59:57 GMT

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

Thank you

RE: Using PDM Mic on nRF9160DK

Einar Thorsrud — Wed, 14 Aug 2019 13:57:30 GMT

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.

RE: Using PDM Mic on nRF9160DK

octvargas — Wed, 14 Aug 2019 13:49:36 GMT

right, but disregarding anything pdm related like pdm_gain and all that, what SHOULD be in there?

RE: Using PDM Mic on nRF9160DK

Einar Thorsrud — Wed, 14 Aug 2019 13:46:51 GMT

I am not sure you need anything PDM related. Since the PDM driver is anyway not fully integrated with Zephyr you have to use the nrfx driver directly. As mentionned earlier PDM is even missing in the device tree (.dts), so you have to tweak it.

RE: Using PDM Mic on nRF9160DK

Einar Thorsrud — Wed, 14 Aug 2019 13:44:08 GMT

I was thinking to gradually check the files in the include hierarchy described in the previous post, between nrfx_pdm.c and nrfx_config_nrf9160.h. At which point is NRFX_PDM_ENABLED no longer defined or no longer set to 1? It could be done with something like the following (untested):

#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

RE: Using PDM Mic on nRF9160DK

octvargas — Wed, 14 Aug 2019 13:35:42 GMT

Einar, a possibly stupid question but what SHOULD my .conf file have in it?

RE: Using PDM Mic on nRF9160DK

octvargas — Wed, 14 Aug 2019 13:13:20 GMT

I'll try that, and yes, to my knowledge I'm using 1.0.0, but out of curiosity how would I check that?

RE: Using PDM Mic on nRF9160DK

Einar Thorsrud — Wed, 14 Aug 2019 12:19:48 GMT

Ah, I see. There no reason to define NRFX_PDM_ENABLED in the main.c file.

Did you put it in nrfx_config_nrf9160? The file holding the implementation of nrfx_pdm_buffer_set, nrfx_pdm.c, includes nrfx.h, which includes nrfx_config.h which includes nrfx_config_nrf9160.h, which is where we set the configuration. So it should be included in that case.

If it still does not work, then perhaps you can print some warnings or similar using, for instance, #warning to track where the definition is set to which value, and where it "gets lost". I have not spotted it, at least.

By the way, are you using NCS 1.0.0?

RE: Using PDM Mic on nRF9160DK

octvargas — Tue, 13 Aug 2019 21:13:37 GMT

i should add, I've also tried include <nrfx_pdm.h> as well

RE: Using PDM Mic on nRF9160DK

octvargas — Tue, 13 Aug 2019 20:40:55 GMT

So, I tried adding your undefine and then define into my main.c file, but that didn't help matters. I'm still getting the same undefined reference error.

I'm including my file, just in case there is a glaring error I'm missingdevzone.nordicsemi.com/.../8473.main.txt

RE: Using PDM Mic on nRF9160DK

octvargas — Fri, 09 Aug 2019 13:58:13 GMT

Thanks Einar,

I'll give it a try and report back

RE: Using PDM Mic on nRF9160DK

Einar Thorsrud — Fri, 09 Aug 2019 12:52:06 GMT

Hi,

I am sorry, it seems I have played too little with nRF Connect SDK. Setting NRFX_PDM_ENABLED in nrfx_config_nrf9160 does not have effect if it is defined somewhere else. Can you try to set it to 1 in prj.conf also/instead? You could also try to replace:

#ifndef NRFX_PDM_ENABLED
#define NRFX_PDM_ENABLED 0
#endif

with:

#undef NRFX_PDM_ENABLED
#define NRFX_PDM_ENABLED 1

Note that PDM is not properly integrated with Zephyr as of now. It is missing in the device tree, so there are no register definitions etc. If you need PDM now you have to add it yourself, unfortunately.

RE: Using PDM Mic on nRF9160DK

octvargas — Thu, 08 Aug 2019 13:37:51 GMT

Hi Einar,

So I did what you suggested

but when still when I re-load and try to build the program it still gives me the same error.

I'm more than a little lost here. Any other help is appreciated.

Thank you