Skip to main content

ArduPilot laser rangefinder (Lua, RNGFND1_TYPE=36)

:::caution Status, checked 2026-11-13

  • Lua script route: works on stock ArduPilot firmware with scripting. In ArduPilot SITL the script decodes a family B centimetre frame correctly. It has not been flight-tested on a flight controller.
  • Native C++ driver: ArduPilot pull request #34983 is open and waiting for review. It is not merged and is not in any firmware release.
  • ERDI modules are not described as supported by ArduPilot on this site, and will not be until upstream merges and documents a driver. Bench-test with propellers off before any flight. :::

Route 1: Lua script (no upstream change needed)​

ArduPilot's rangefinder backend RNGFND1_TYPE=36 takes distances from a Lua script. The ERDI script reads the module on a scripting serial port and hands the distance to the backend.

Requirements on the flight controller:

  • Flash larger than 1 MB. Pixhawk 6C/6X, Cube Orange and H743-class boards qualify. F4 boards and 1 MB boards do not run scripting (ArduPilot wiki: Lua scripts need at least 2 MB flash, 80 kB RAM and an SD card).
  • An SD card for the script.

Steps:

  1. Wire a free UART: module TX to flight controller RX, module RX to TX, common ground. Power the module from a supply that fits its datasheet. H series modules need 9 to 36 V and must not use the 5 V telemetry pin. See wiring and power.

  2. Set parameters and reboot:

    ParameterValue
    SCR_ENABLE1
    SCR_HEAP_SIZE150000 or more
    SERIAL2_PROTOCOL28 (Scripting), for the port you wired
    RNGFND1_TYPE36 (Lua scripts)
    RNGFND1_ORIENT25 (downward)
    RNGFND1_MIN, RNGFND1_MAXmetres, from the datasheet range of your model

  3. Copy erdi_lrf.lua to APM/scripts/ on the SD card (Mission Planner can upload it over MAVFTP) and reboot.

  4. Set the script parameters for your model, then reboot again:

ModelERDI_MODEERDI_BRERDI_UNITERDI_LENERDI_OOR
LR1000E21115200n/an/an/a
LR1000E41115200n/an/an/a
LR1200E21115200n/an/an/a
LR1200E41115200n/an/an/a
LRF1200A11115200n/an/an/a
SPD1200N01115200n/an/an/a
SPD1200N21115200n/an/an/a
SPD1200N41115200n/an/an/a
LR1500E21115200n/an/an/a
LR1500E41115200n/an/an/a
LR2000E21115200n/an/an/a
LR2000E41115200n/an/an/a
LRF3000A11115200n/an/an/a
LRF10VB04608000.001465535
LRF22VB04608000.001420000
LRF50VB04608000.001450000
LRF50H04608000.01465535
LRF100H04608000.01465535
LRF200H04608000.01465535
LRF300H04608000.01465535
LRF600H04608000.01465535
LRF1500H04608000.01516777215

Other script parameters: ERDI_SP (index of the scripting serial port, 1 = first), ERDI_POLL_MS (family A poll period, 50 to 1000 ms). Full reference: parameters.md.

  1. Compare the RFND log entry or the ground-station rangefinder display with a tape measure. Checklist: hardware test checklist.

Limits you should know​

  • ArduPilot declares the rangefinder as having no data if nothing arrives for 500 ms. Family A modules polled at 1 to 2 Hz at long range can drop in and out of "No Data". Poll faster or use a streaming model.
  • The scripting heap and CPU use were not measured over a long run. Treat long-duration stability as untested.
  • Only the family B centimetre frame has been exercised in SITL (see below). The millimetre frames of the VB series, the 5-byte LRF1500H frame and family A polling have not.

What was verified, exactly​

ArduPilot SITL (the PR branch build, based on ArduPilot master of 2026-11) was run with RNGFND1_TYPE=36 and the unmodified erdi_lrf.lua with its default parameters (family B, 4-byte frame, centimetres, out-of-range marker 65535). A feeder sent synthetic frames to the simulated serial port:

  • 1234 cm frames at 100 Hz: the flight controller reported a DISTANCE_SENSOR of 1234 cm (12.34 m).
  • The marker 65535: reported as 5100 cm, which is RNGFND1_MAX (50 m) plus 1 m, the backend's out-of-range-high value.
  • Stream stopped: PreArm: Rangefinder 1: No Data.
  • 184 DISTANCE_SENSOR messages in the run, no Lua errors.

The synthetic frames are not a physical module on a flight controller. Evidence files: SITL evidence.

Route 2: native driver (pull request, not merged)​

PR #34983, "AP_RangeFinder: add ERDI VB and H series serial rangefinders", adds a C++ backend and a SITL simulator:

  • RNGFNDx_TYPE = 49: LRF10VB, LRF22VB, LRF50VB (millimetres)
  • RNGFNDx_TYPE = 50: LRF50H, LRF100H, LRF200H, LRF300H, LRF600H (centimetres)

Its automated checks pass and it is waiting for a maintainer review. A factory bench run of an LRF22VB and an LRF50H through a USB-TTL adapter is in the bench evidence. Flight-controller logs are still to come. Native drivers merged now would first ship in the next ArduPilot release series.

Option 3: companion computer​

A Raspberry Pi or Jetson can read the module and send MAVLink DISTANCE_SENSOR to the flight controller, which works on any board: see Raspberry Pi and Jetson and PX4.