nRFX based PDM to PCM implementation (I2S example)

[Nikhil Komalan]

Hello,

I am currently interfacing my nRF52840 DK with i2S based MP34DT05 sensor. I am using nrfx i2s driver's for interfacing with sensor. I am using master clk of 2MHz, LCLK 16KHZ. 

My sensor output PDM data. In my project I am recording audio samples on left channel, so I am currently getting 2*16bit of left data per 32bits as shown in nrf docs. I have got 16bit recorded samples in buffer, but to how to convert this pdm data in pcm format. 

Normally we need to divide the PDM data with a decimation factor, but in I2S we already are dividing the bit sampling rate with ratio value. So is the output from the I2S itself is decimated PCM ?  

Or can anyone give a example of how to convert the PDM to PCM data. Any sort of help is dually appreciated. 

[Nikhil Komalan]

Okay trying this out

Audun said:

Note that it is probably best to define a struct for your audio data, which contains the int16_t audio buffer, plus the fifo_reserved data field, plus whatever else might be useful.

wanted to know, why you suggested int16 because in my current program  my buffer is uint16.

[Audun]

Btw, I realized I linked to and old version of the documentation, but these function names have not changed as far as I know. Also, note that in the PDM ISR/handler, you must used timeout value K_NO_WAIT