Lidar Lite v3 HP not detected on Pixhawk 4

I am some trouble getting Copter 4.0.3 to recognize the lidar lite v3 HP that is installed on the copter I am working on.

I get the following message in mission planner: PreArm: Rangefinder 1 was not detected

Here are the parameters I have the Lidar set up with.

There is also an IR LOCK on the same I2C bus that appears to be recognized.

When I put my phone’s camera under the Lidar lite, I don’t see a blast of IR light from an LED or laser, so I am not sure if the unit is getting power or not (I will check this with a voltmeter shortly)

Lidar is getting power. Measures out to 4.88V.


It’s powered from the internal 5V rails on the PH4. We’re doing up a wire harness to fix that right now, as we suspected that was part of the problem.

update: harness changed to support power from external source. The unit is getting 5.24V now. No change to behavior.

note: I am using I2C for the interface.

Phone cameras sometimes don’t have IR filters on them which makes checking if the lidar is on easier. I had an issue with the 1 kOhm resistor. I ended up using a 660 resistor.

  • it’s on an I2C splitter (the I2C line going back to the Pixhawk 4 has GND/SDA/SCL only, I removed the +5V pin from the connector)
  • Power is from a dedicated that powers only the lidar lite and an IR LOCK camera
  • If I remove the IR LOCK camera I observe no change in behavior
  • I checked the wiring harness for SCL to SDA crosses and did not find any issues
  • with the lidar only the I2C bus has no traffic between pixhawk 4 and lidar

I looked at the lidar with my phone camera and didn’t see any evidence of the IR light source running, so it’s not clear the unit is powered up.

We got a spare regular Lidar Lite 3 (not the HP) and swapped that into the system and it appears to work, so it looks like we had a dead lidar on our hands… We’re gonna put the setup back together and test the whole system and see if we get the IR LOCK to work.

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Oddly enough, the IR LOCK and the LIDAR can’t share the same I2C bus, which is annoying.