LightWare GRF250 / GRF500

The LightWare GRF250 and GRF500 are long-range lidar-based rangefinders. Both models support serial (UART) communication and provide accurate distance and signal-strength data at configurable update rates.

  • GRF250: 0.2 m – 250 m range

  • GRF500: 0.2 m – 500 m range

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Note

Support for the LightWare GRF250 and GRF500 sensors was added in ArduPilot 4.7 and later.

Serial Connection

The GRF sensors communicate via UART using 3.3 V or 5 V logic levels. Connect the TX of the Lidar to the RX of the autopilot UART port, and the RX of the Lidar to the TX of the same port. Also connect GND and 5 V to power the sensor.

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Example (SERIAL4):

If the GRF is connected to the autopilots’ SERIAL4 port and it is the first rangefinder:

If instead you are using the SERIAL2 port, set SERIAL2_PROTOCOL = 9 and SERIAL2_BAUD = 115.

Power note: The GRF sensors can draw higher current than typical serial peripherals. Check your flight controller’s 5 V peripheral rail limits — an external 5 V supply may be required.

Additional GRF-specific Parameters

When RNGFNDx_TYPE is set to 45 (LightWareGRF), the Serial port protocol is set to 9, and the autopilot is rebooted, the following additional parameters become available:

  • RNGFNDx_GRF_RET: Selects which return type to use (0: FirstRaw, 1: FirstFiltered, 2: LastRaw, 3: LastFiltered).

  • RNGFNDx_GRF_ST: Sets the minimum acceptable return signal strength in dB. Returns weaker than this value are ignored (0 disables filtering).

  • RNGFNDx_GRF_RATE: Sets the sensor update rate in Hz. GRF250 supports 1–50 readings per second, while GRF500 supports 0.5–10 readings per second.

Testing the Sensor

You can view the live distance readings in Mission Planner → Flight Data → Status tab, under the field named “rangefinder1” (or rangefinder2 / 3 for additional sensors).

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If values remain at zero, verify serial wiring, baud rate, and power supply.