Microphones

Microphone Array on MATRIX Creator

Mic Position

Usage

Driver installation

Follow the instructions below for allowing your MATRIX Creator to register as a microphone for your Raspberry Pi.

curl https://apt.matrix.one/doc/apt-key.gpg | sudo apt-key add -
echo "deb https://apt.matrix.one/raspbian $(lsb_release -sc) main" | sudo tee /etc/apt/sources.list.d/matrixlabs.list
sudo apt-get update
sudo apt-get upgrade

A reboot will be required after following the steps above.

sudo reboot

The next commands will install the MATRIX kernel modules, overriding the stock Raspbian kernel.

sudo apt install matrixio-kernel-modules

A second reboot will be required.

sudo reboot

Check If Everything Works

Your Raspberry Pi should now treat your MATRIX Creator as a regular microphone. You can test this by using the following commands to record and play a 5 second long audio file on your Raspberry Pi.

Be sure to have something connected to the Raspberry Pi's audio output.

arecord recording.wav -f S16_LE -r 16000 -d 5
aplay recording.wav

ALSA Configuration

The microphones can be grabbed using ALSA. Multiple libraries that support ALSA use these configurations to read microphone data with ALSA.

Device name - hw:2,0

Rates(Hz) - 8000 12000 16000 22050 24000 32000 44100 48000 96000

Channels for each microphone - 1 2 3 4 5 6 7 8

Audio Specifications

Sample Rate: 8 to 96 kHz

Bit Depth: Signed 16 bit

Position [x,y] of each mic in the array (mm)

Mic X Y
M1 20.0908795 -48.5036755
M2 -20.0908795 -48.5036755
M3 -48.5036755 -20.0908795
M4 -48.5036755 20.0908795
M5 -20.0908795 48.5036755
M6 20.0908795 48.5036755
M7 48.5036755 20.0908795
M8 48.5036755 -20.0908795

Connection to the FPGA

You can check the physical connection between the FPGA and other components in creator.ucf

Mic FPGA pin PDM_Data
M1 P45 pdm_data<0>
M2 P46 pdm_data<1>
M3 P47 pdm_data<2>
M4 P58 pdm_data<3>
M5 P59 pdm_data<4>
M6 P64 pdm_data<5>
M7 P65 pdm_data<6>
M8 P44 pdm_data<7>
CLK P47 pdm_clk