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Published in 2015-09-05 15:33:02       


Garmin LIDAR-Lite V3 Software&Document Download

update: 2017.01.17,

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PULSEDLIGHT LIDAR-Lite V2 Download

update: 2015.09.05,



Documents:

2016-10-24 10:25:45

Original text

http://ardupilot.org/copter/docs/common-rangefinder-lidarlite.html

Connecting to the Pixhawk via I2C

Warning

If you have a LIDAR-Lite that has a manufacture date label prior to February 2015 there are I2C interface communications issues that will cause unreliable operation of the sensor with Pixhawk and will cause your vehicle to crash. When using these versions of LIDAR-Lite please use the PWM alternative listed below for best results.

The cable is configured with a 6-position Molex CLIK Mate connector on one end and tinned leads on the opposite end. You will need to solder the tinned ends to a modified DF13 4-pin I2C cable as shown below.

The power to the rangefinder should be supplied from a separate external BEC as shown in the diagram below.

../_images/RangeFinder_LIDARLite_Pixhawk_v2_Capacitor_3.jpg

LIDAR-Lite/PixhawkConnection Diagram

Note

The low pass filter shown in the diagram is required for first generation hardware (for hardware with manufacture dates prior to February 2015) - a schematic and PCB design are provided here. These should not be required in later versions of the LIDAR Lite (at which point the diagram will change as shown below:

../_images/rangefinder_lidarlite_pixhawk_v2.jpg
../_images/rangefinder_lidarlite_circuit_diagram_for_next_generation.jpg

You may wish to also purchase an I2C splitter so that you can continue to connect an external GPS/Compass module.

Note

It is important to ensure that the ground from the BEC is connected to the ground on the servo rail.

Connecting to Pixhawk via PWM

As of the 3.3.x release of Plane and Copter you can connect your Lidar via PWM as an alternative to I2C. This works around a number of bugs in the I2C interface for the Lidar. The bugs include generating spurious pulses on the I2C bus and lockups of the Lidar in flight.

To connect via PWM you need to connect 4 pins on the Lidar to the PWM rail of the Pixhawk. The connections are as follows:

LIDAR-Lite Pin Pixhawk Pin
J1 CH6 Out V+
J2 CH6 Out Signal (internal pin 55)
J3 CH5 Out Signal (internal pin 54)
J4 (not used)
J5 (not used)
J6 Ch6 Out Ground
../_images/side_back.jpg

You need a resistor between J3 and ground. The exact value of the resistor isn’t critical, somewhere between 200 Ohm and 1kOhm will do. Testing for the development of the driver was done with a 470 Ohm resistor. The resistor is what tells the Lidar to start taking a reading, so connecting a resistor between pin 3 and ground tells the Lidar to go into continuous acquisition mode.

Here’s a picture of the necessary cable, with the resistor shown before being covered by heat-shrink tubing:

../_images/lidar_lite_cabling_and_resistor.jpg

You then need the following parameters set to enable the PWM driver:

  • RNGFND_TYPE = 5
  • RNGFND_STOP_PIN = 55
  • BRD_PWM_COUNT = 4
  • RNGFND_SCALING = 1
  • RNGFND_OFFSET = 0

The use of pin 55 as the stop pin is just a suggestion, not a requirement. It connects to the enable pin on the Lidar, and allows the driver to reset the Lidar if it stops providing readings.

The use of pin 54 for the PWM signal is required, and only FMU AUX5 (pin 54) can be used due to the internal timer routing of the Pixhawk.

Note: when using LIDAR-Lite in PWM mode please keep the following in mind:

  1. You need to have a battery/ESC plugged in. (in PWM mode, the LIDAR-Lite gets its power from the servo rail, which is powered by the ESC)
  2. On the ground station side, APMPlanner currently does not display the data, but Mission Planner does. Fixes are on the way.
  3. Make sure the LIDAR is not right on a table and is at least 20cm or so from the nearest surface. Otherwise, it will display 0 distance (which is correct!)
  4. By default, on Copter if you have the LIDAR enabled, it will check LIDAR range on startup. To pass the check, lift the vehicle up at least 50cm. Don’t tip it over too much because the check is a bit sensitive, it needs to see a range of between 50cm ~ 2m but nothing longer than 2m. If it sees a range longer than that, it’ll never pass unless you reboot the board (nicer solution to this coming soon!). The check can be disabled by setting ARMING_CHECK to Skip Param/Sonar.

Optional Power Saving

When using the PWM driver you can optionally set RNGFND_PWRRNG to a terrain height in meters above which the Lidar will be disabled to save power. When the terrain data indicates that the vehicle is above that height the RNGFND_STOP_PIN will be used to disable the Lidar. This saves around 100mA of current.

Your GCS must provide terrain data for this to work.

2016-12-13 07:01:57
2017-01-14 03:53:14

we would free provide the accessories package to use LIDAR Lite V3. The accessories can let LIDAR Lite to work with pixhawk or Arduino board.


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