During mono audio capture over PDM, we observed a current draw of about 1.5 mA.

[Adityanath Pandey]

Our setup:

• Board: nRF5340 DK
  
• SDK: NCS v2.6.2
  
• Microphone: MMICT5837-00-012
  
• Interface: PDM
  

During mono audio capture over PDM, we observed a current draw of about 1.5 mA.
My questions are:

• Is there any way to reduce this current consumption further?
  
• How much current does the PDM peripheral itself typically draw in mono mode on the nRF5340 (excluding microphone current)?

[Turbo J]

Expected behaviour.

You need to keep the HF clocks running in order to be able to capture the audio data. That keeps a fairly sizeable portion of the digital chip area powered on and not being able to sleep at all.

[Adityanath Pandey]

We read microphone data by calling dmic_trigger(dmic, DMIC_TRIGGER_START) before starting,

and dmic_trigger(dmic, DMIC_TRIGGER_STOP) afterward. This process is repeated every 100 ms.
However, when we parse the recorded file, we hear a “beep” sound.

My question: How long does dmic_trigger() take to execute, and could this delay be the cause of the beep sound?

[Edvin]

From where do you call dmic_trigger()? In an interrupt? And what sort of buffer are you using? Single? Double?

Best regards,

Edvin

[Adityanath Pandey]

We are not calling dmic_trigger() from an interrupt.

We use it in our application code, before and after reading data. The actual microphone data is obtained through the dmic_read() API.
Our read function looks like this:
int mic::readdata(void *pcm_data, uint16_t *len) {
int ret;
void *buffer;
uint32_t size = 0;

ret = dmic_read(dmic, 0, &buffer, &size, READ_TIMEOUT);
if (ret < 0) {
LOG_ERR("read failed: %d", ret);
return ret;
}

memcpy(pcm_data, buffer, size);
*len = size;

k_mem_slab_free(&mem_slab, buffer);

return ret;
}

[Edvin]

And from where are you calling mic::readdata()?

Best regards,

Edvin

[Adityanath Pandey]

I have created one thread from where mic::readdata() has been called.

[Adityanath Pandey]

 However, according to the nRF5340 datasheet, the PDM peripheral should consume only about 1.25 mA.so current with easyDma?

[Edvin]

Adityanath Pandey said:

PDM peripheral should consume only about 1.25 mA

Can you point me to where it says? I couldn't find it. 

However, it is possible that this number is for the PDM only, not including the current for the HFXO running, and the CPU running to handle the incoming data.

How do you measure the current consumption, by they way? Are you using the PPK2?

Best regards,

Edvin

[Adityanath Pandey]

I have referred to this link : https://docs.nordicsemi.com/bundle/ps_nrf5340/page/chapters/current_consumption/doc/current_consumption.html

I am not using PPK2 kit but using DMM6500 (6 1/2 Digital multi meter ) for measuring current.