Multi threads ADC read and saving it to a local file

[Alirezaaraby]

Hi, i want to make an audio recorder with raspberry pi pico and max 9814. But the problem is when i want to save the recorded audio into a .wav file it loses some parts of the audio because it runs on one core and i want to write a code to handle the process of saving data on another core.

[peterhinch]

It could be difficult to make this work.

I would consider an alternative approach: a MEMS microphone with an I2S interface such as this one. The RP2 has support for i2s and there is an asynchronous API. It should therefore be possible to concurrently acquire data and save it using suitable buffering and asyncio.

This is something I intended to do, but to date I haven't found time.

[Alirezaaraby]

thanks for your help. I bought this https://www.adafruit.com/product/3421 microphone but there's no tutorial on the internet for connecting it to rpi pico. can you give me a hand on how I can wire it?

[ned-pcs]

Take a look at https://github.com/miketeachman/micropython-i2s-examples also.
And read the datasheet: https://www.knowles.com/docs/default-source/default-document-library/sph0645lm4h-1-datasheet.pdf
Note especially that BCLK must be 64x of LRCLK, so the microphone should be set up as a 32-bit stereo, but only alternate 32-bit samples will have actual data.

i2s = I2S(1, sck=Pin(0), ws=Pin(1), sd=Pin(2), mode=I2S.RX, bits=32, format=I2S.STEREO, rate=22050, ibuf=40000) # create I2S object
i2s.readinto(buf)          # fill buffer with audio samples from I2S device

• BCLK on the microphone is connected to the sck pin on the Pico.
• DOUT on the microphone is connected to the sd pin on the Pico.
• LRCLK on the microphone is connected to the ws pin on the Pico.

[Alirezaaraby]

Thanks, it worked