Microphones

Microphone Array on MATRIX Voice

Mic Position

Usage

Driver installation

Follow the instructions below for allowing your MATRIX Voice 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 the MATRIX packages above are installed.

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 Voice 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 specs

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 00.00 0.00
M2 -38.13 3.58
M3 -20.98 32.04
M4 11.97 36.38
M5 35.91 13.32
M6 32.81 -19.77
M7 5.00 -37.97
M8 -26.57 -27.58

Connection to the FPGA

Mic FPGA pin PDM_Data
M1 E6 pdm_data<0>
M2 B8 pdm_data<1>
M3 A8 pdm_data<2>
M4 C7 pdm_data<3>
M5 A7 pdm_data<4>
M6 A6 pdm_data<5>
M7 B6 pdm_data<6>
M8 A5 pdm_data<7>
CLK B5 pdm_clk