Overview

This branch is a template for implementing microphone audio applications on the SAME54 Curiosity Ultra + wm8904 codec. Audio input is formatted as 16-bit PCM (signed Q1.15) at 16kHz.

Firmware

The firmware can be configured for two different build types: (1) a simple level meter and (2) a UART data streamer; this selection can be made by modifying the BUILD_APPLICATION_TYPE value in app_config.h

APPLICATION_TYPE_LEVEL_METER

This application just outputs the measured signal level over UART at a baud rate of 921600.

APPLICATION_TYPE_DATA_STREAMER

This application will stream data over UART:

• Transmits at a baud rate of 921600
• Data is sent in frames containing AUDIO_BLOCK_NUM_SAMPLES samples (see app_config.h)
• Frames are separated by a header byte (0xa5) and footer byte (0x5a)
• Frame size can be configured by modifying AUDIO_BLOCK_SIZE_MS in app_config.h.

The readserial.py script described below can be used to capture the audio data.

Capturing Streaming Audio

The readserial.py script provides an example of how to parse out this data and save it to a .wav file:

• Requires python 3

• Requires a few python packages: to install, run:

  pip install -r requirements.txt

• Script can be run interactively via IPython or Jupyter notebook, or directly from the terminal using the following call format:

  readserial.py <com-port> <baud-rate> <burst-size> <num-samples>

  For example:

  readserial.py COM7 921600 512 16000

• Running the script will stream audio from the device and save it to a wav file named readserial.wav.

Known Issues

• Occasionally I've found that the board needs to be reset after programming for the program to work. Adding delay after reset seemed to fix this (Project Properties -> EDBG -> Diagnostics -> Additional delay after reset).