After some struggles, I finally added complete audio recording and playback functionality to my AutoAnalogAudio library for nRF52840 devices. It was originally designed for the Arduino Due, but I've expanded it to include other devices.
The code has been tested on the XIAO BLE 52840 Sense, but should work on the Feather 52840 Express and similar boards based on any nRF52x chip.
It supports 16, 24, 32 & 44kHz sample rates, stereo/mono and 8 or 16-bit playback using either PWM (lower quality) or I2S (higher quality) playback.
Recording is supported via PDM microphone at the same sample rates @ 16-bits.
I've included some platform specific example files for the nRF52x devices, so if an onboard microphone is present, users only need to connect a regular (analog) or I2S amplifier for testing, no other hardware is required.
Documentation is available at Auto Analog Audio: Automatic Analog Audio Library for Arduino
Installation via Arduino Library Manager
The nRF52x devices have a Bluetooth capable radio built-in, so users can create custom audio applications using either that or operate the radio at OSI layer-2 for even faster communication using my nrf_to_nrf library which is interoperable with nRF24L01 radios using the RF24 library.
I'm loving this chip! It is soo nice to program and play with! Just thought I would share my work.