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Communications — UART Output

The board's interface to your system is a single UART on the host connector (J7). With the default firmware it emits a plain ASCII distance stream that any flight controller or onboard computer can read — this page is the complete spec for that stream.

Alternate firmware changes this link's protocol

The ACO firmware variant (beta) makes this same UART speak MAVLink v2 at 115 200 baud (running collision avoidance on-board and sending OBSTACLE_DISTANCE to a flight controller) instead of the ASCII stream below.

Physical

  • Connector: J7 (see Hardware → Host UART). Board TX (pin 3) → host RX, GND (pin 4) → host GND.
  • Format: 8 data bits, no parity, 1 stop bit (8N1), no flow control.
  • Direction: one-way (board → host).

Baud rate — important

Configure your host for ≈921 600 baud.

  • 921 600 is chosen because it's the fastest rate typical flight-controller UARTs and USB-UART adapters receive reliably.
  • ⚠️ Some older material / a boot banner may mention 115 200 — that's stale. Use 921 600.

Wire format (ASCII)

For every sensor with new data, the board prints a header line then eight rows of eight integers. Distances are in millimetres; 0 means invalid / no return (see Measurement validity).

--- CH<n> ---
 1234  1230  1228 ...   (row 0: 8 space-padded integers, mm)
 ...                    (rows 1..7)
  • Header: literal --- CH followed by the channel digit 0–7 and ---.
  • Each of the 8 rows: 8 integers → an 8×8 = 64-zone grid for that channel, row-major, in the sensor's own frame.
  • Frames stream at the ranging rate (15 Hz per sensor); channels are printed round-robin as each sensor reports new data.

So the full stream is, per channel, an 8×8 matrix of millimetre distances — one matrix per sensor, updating at 15 Hz.

Reading it directly

Any serial terminal or a few lines of code will do — no special tooling:

# any serial terminal, 921600-8N1, e.g.
screen /dev/tty.usbserial-XXXX 921600
#   or:  minicom -D /dev/ttyUSB0 -b 921600

To turn the grids into 3-D points or obstacle data, see Integration.

Measurement validity

The board emits 0 for any zone that is not a real measurement (no/low signal, out of range, etc.). Treat 0 as "no return", never as "obstacle at 0 mm". All non-zero values are valid distances in millimetres.