Recording and Playback of Audio on the XIAO NRF52840 Sense - Auto Analog Audio

 Recording and Playback of Audio on the XIAO NRF52840 Sense

Auto Analog Audio Library

So I've been struggling with the I2S interface of the NRF52 devices, and have given up for the time-being trying to get it to work properly. In the meantime I've made some decent headway with the PWM interface and reproducing audio that way. This is similar to the TMRpcm library for AVR devices, which also uses Pulse-Width-Modulation to reproduce audio. 

So far the AutoAnalogAudio library is in a very basic but functional state with an included example to demonstrate how to record and playback audio on the XIAO 52840 Sense. It is designed to input audio from the PDM microphone directly and output using Pin5 of the XIAO board via PWM. The audio signal is 16-bit, 16kHz audio, so of reasonable quality, and cannot currently be modified. The code is still in its infancy.

This makes it easy to record and transmit audio over radio link, since with the nrf_to_nrf radio library, users can broadcast the audio to another device very easily. 

There are still a few problems with it, mainly some synchronization issues, which result in a clicking sound when audio is fed directly from the microphone into the PWM output (Amp & Speaker). I'm not quite sure how to resolve it currently, so will leave things as-is. Update: Adjusting the timers slightly to make the PWM a bit slower than PDM input results in a smooth output signal.

A new release will not be made for a little while, so to try it out, just install the AAAudio library directly from ZIP. See GitHub at  https://github.com/TMRh20/AutoAnalogAudio