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Hi all,

I am new to this forum but I have been a reader for a few years now. I am having multiple issues with Lidar-Lite V3 and any help would be greatly appreciated.

I am customizing a medium size X8 multirotor (40 lbs). I recently obtained 2 Lidar-lite V3 from Sparkfun and both are having the same issues so I assume the lidar sensors are not defective.

The first issue is a 9.5 constant offset in Lidar-lite V3's altitude readings using I2C connection with Pixhawk 2.1 on Mission Planner. The lidar displays the correct changes in altitude correctly but the altitude readings always offset by a constant of +9.5. I have followed this document to make my I2C wirings and settings:  https://www.lambdrive.com/depot/Robotics/Controller/Firmware/ArduPilot/LIDAR-Lite.html. I have even added a ground wire between the Pixhawk's I2C port and its servo output rails just to be sure. It still gives an offset of roughly +9.5.

I have seen some pages claimed (end of 2018) that there was an incompatible issue with the Lidar's driver and the Arducopter 3.6.x when using I2C connection. Has the issue been fixed yet?

After a couple days, I gave up on I2C and gave PWM connection a try. I followed the wiring instruction from the below picture and it seems that the lidar is working properly ..... The PWM connection gives more accurate altitude data on the ground. However, it becomes less reliable once the multirotor gets above 8 meters. The log reveals that the range finder's distance readings is very spiky above 10 meter altitude. The lidar seems to cut in and out. Although I have set EK2_ALT_SOURCE=0 to make Barometer sensor the main altitude sensor source, the Pixhawk still seemed to be using the lidar's spiky data for its calculations. Once the aircraft got above 8 meters in AltHold or Loiter mode, the aircraft's aircraft seems to be drifting up and down by +/- 2 or 3 meters. The drifting only stopped when I stepped in and corrected the throttle. I flew the rest of the flight in Stabilize mode. 

I have attached a telemetry log to this discussion for anyone's review. 

I have made the following changes to Pixhawk's parameters:  

BRD_PWM_COUNT = 4 
RNGFND_TYPE = 5 #PWM Driver 
RNGFND_PIN = 54 #PWM input = Pixhawk AUX5 
RNGFND_RMETRIC = 1 
RNGFND_MIN_CM = 20 
RNGFND_MAX_CM = 800
RNGFND_OFFSET = 0 
RNGFND_GNDCLEAR = 5
RNGFND_STOP_PIN = 55 # Pixhawk AUX6 
RNGFND_PWRRNG = 20 # Put Lidar to sleep above 20m  
RNGFND_SCALING = 0.8
RNGFND_GAIN = 0.6 
EK2_ALT_SOURCE = 0
EK2_RNG_USE_HGT = 50 
EK2_ALT_M_NSE = 3 

EK2_RNG_M_NSE = 0.5

EK2_TERR_GRAD = 0.1
EK2_RNG_I_GATE = 500 

PWM Connections (Note: I am using a Pixhawk 2.1 instead of the Pixhawk 1 in the below picture)
 

2019-02-15 10-12-28.tlog