MicArray UAC Drive Board MA-USB8 — User Guide

Product overview

MA-USB8 is a USB audio + serial interface drive board designed for MicArray microphone modules. It forwards the array’s audio (via UAC2.0, 8 channels) and sends soundfield hotmap frames (via CDC ACM or UART) to a host PC or MCU. Common use cases include voice capture, noise suppression, beamforming, and soundfield visualization.

• UAC2.0 (USB Audio Class): 8 channels, PCM S16_LE, 48 kHz
• CDC ACM (USB virtual COM): 16×16 raw hotmap frames
• UART: 16×16 raw / HEX + pseudo-color hotmap frames at 2,000,000 bps (suitable for MCUs)

This document is a user guide for MA-USB8. It covers connection, device verification, audio capture, beamforming, how to read/parse hotmap frames, and common troubleshooting.

Quick start

Hardware and basic setup

1. Use a data-capable 5V USB cable.
2. Connect MA-USB8 to your host PC or to your MCU board via USB/USB2TTL.
3. Choose a mode:
   • Preferred: USB (UAC2.0 audio + CDC ACM serial) — on PC you can get multi-channel audio and hotmap frames together.
   • Alternate: UART / USB2TTL (2,000,000 bps) — for MCU/embedded environments to get hotmap frames (HEX/pseudocolor) only.

We recommend installing Audacity on your PC for testing/recording.

Before proceeding, check:

• That the USB cable is firmly connected and the board is powered (check LEDs).
• That the device appears in your system (Linux: /dev/ttyACM0 or /dev/ttyUSB0; Windows: look for MA-USB8 audio/CDC device in Device Manager).

Verify the device (Linux)

• After plugging in, run:
  • dmesg | tail — you should see /dev/ttyACM0 and SipeedUSB MicArray.
  • lsusb — to inspect device IDs.
• Check audio devices with:
  • arecord -l — you should find an 8-channel UAC device.
  • pactl list short sources — PulseAudio users can check sources.

Verify the device (Windows)

Open Device Manager and confirm the device appears as a multi-channel audio device and a CDC ACM serial port. Use software that supports multi-channel UAC capture (e.g., Audacity configured with WASAPI) to record all 8 channels.

Record 8 channels (UAC2.0)

Linux (CLI)

Find the card/device and record 8 channels using arecord:

arecord -l  # find the card / device
arecord -D hw:1,0 -f S16_LE -c 8 -r 48000 -t wav -d 10 test_8ch.wav

Extract and play one channel (e.g., CH6):

sudo apt install sox
sox test_8ch.wav ch6.wav remix 7  # sox uses 1-based channel indexing; `remix 7` extracts CH6 (zero-based→1-based)
aplay ch6.wav

Notes:

• Device indexes and channel mapping may vary between systems and drivers. Use arecord -l / aplay -l to confirm hw index and channel mapping.
• If Windows only shows 2 channels, use WASAPI in Audacity or use Linux for full multi-channel capture.

Audacity (GUI)

1. Open Audacity → Edit → Preferences → Devices, and select MA-USB8 as the recording device.
2. Choose the number of channels (8) in the recording options.
3. Record and inspect the tracks; you can solo or export an individual channel as needed.

Windows: Use WASAPI to enable 8-channel capture
Windows requires using WASAPI in Audacity to expose all 8 channels — choose the MA-USB8 device under WASAPI and select 8 channels.

Beamforming demo

MA-USB8 supports 12 beamforming directions: 0..9, A, B (each step = 30°).

To point the beam to CH0 (0°) and monitor the beamformed output on CH6:

1. Open the CDC ACM serial device (e.g., /dev/ttyACM0) with a serial terminal:

minicom -D /dev/ttyACM0 -H

2. Type a single character (e.g., 0) to set the beam direction to 0°. The beamformed audio will be output on CH6.
3. Record or play CH6 and confirm that sound from the selected direction is amplified and other directions are suppressed.

Note: 0..9, A, B map to angles 0°, 30°, …, 330°.

Observe hotmap frames (CDC ACM / UART)

The board outputs hotmap frames via CDC ACM (/dev/ttyACM0) or via UART (/dev/ttyUSB0 at 2,000,000 bps).

Quick check with minicom / picocom

• CDC ACM (raw):

minicom -D /dev/ttyACM0 -H

• UART (picocom raw/hex):

picocom -b 2000000 --imap 8bithex /dev/ttyUSB0

• In picocom, press F and then C to switch to HEX + color map (some versions/devices).

(Developer note: use hexdump -C or cat /dev/ttyACM0 | hexdump -C -v | head -n 20 to validate frame structure manually.)

Quick serial commands (user cheat sheet)

• Set beamforming direction: send 0..9, A, or B to the serial port; CH6 will be the beamformed output.
• LED on/off: e (off) / E (on).
• Toggle 16×16 ASCII hotmap print: f / F (UART only).

Other developer-level commands are shown in the Developer Reference section.

Troubleshooting

• Windows shows only 2 channels: This is either a Windows driver limitation or your recording software. Use WASAPI in Audacity or switch to Linux for full 8-channel capability.
• Cannot access serial device: user permission issue — add your user to the plugdev group or create a udev rule (see Developer Reference):

sudo usermod -a -G plugdev $USER
# Log out and log in again for the group change to take effect

• CDC ACM does not output frames: Confirm the board is in CDC ACM + UAC modes (not only UAC). Close other applications that may occupy the serial port.
• UART output appears garbled: Ensure 2000000 bps selection; use picocom -b 2000000 or minicom -b 2000000. On Windows, ensure the correct USB-serial driver for your adapter (e.g., CH340/CH341/CH552) is installed.

Firmware

Download the firmware from the assets and follow the combo8 firmware update guide:

Developer Reference (protocol, code examples, full command list)

Hotmap Frame Format

Total packet length = 16 + 256 = 272 bytes. The header is used for frame alignment and detection; payload is the 256-byte matrix of intensity values.

Full command table

udev & Permission (Linux)

Create a udev rule if needed (replace vendor/product with your device’s lsusb IDs):

# /etc/udev/rules.d/99-ma-usb8.rules
SUBSYSTEM=="tty", ATTRS{idVendor}=="XXXX", ATTRS{idProduct}=="YYYY", MODE="0666", GROUP="plugdev"
# Example (Sipeed vendor id)
SUBSYSTEM=="tty", ATTRS{idVendor}=="359F", MODE="0666", GROUP="plugdev"

Serial/USB Notes

• CDC ACM (/dev/ttyACM0) is bound to the Linux cdc_acm driver. If hotmap frames don’t appear, ensure the device is not held by another program.
• UART (/dev/ttyUSB0) typically uses USB-to-serial adapters (CH34x/CH340/CH552); install proper drivers on Windows if necessary.

That’s it — this English translation mirrors the Chinese guide and preserves the commands, examples, and images.