Rangefinder

LIDAR-lite

The I2C interface of non-blue-label Lidar-Lite (v1) devices has stability limitations and all silver-label generations of Lidar-Lite sensors are therefore excluded from the I2C interface. The use of the PWM interface (as detailed below) is advised for these sensors. The blue label (v2) devices can exhibit a constant offset if powered on with less than 5V under some conditions. This is currently (Q4/2015) under investigation by the manufacturer and potentially can be resolved by adhering to specific operational conditions. The recommended robust setup is a v1 device interfaced via PWM.

PWM Interface Wiring

Pixhawk AUX servo pin Lidar-Lite pin Comment
AUX row 5 (bottom) 3 / PWM PWM input of the Lidar Lite. Needs a 470 Ohm pull-down (to GND)
AUX row 6 (center) 1 / +5V Power supply
AUX row 6 (top) 6 / GND Ground
AUX row 6 (bottom) 2 / RESET Reset line of the sensor

PWM usage

To use the Lidar-lite set the param SENS_EN_LL40LS to 1 and reboot.

To test/debug the Lidar-lite, connect to nsh and try:

  pwm_input start
  pwm_input test
  
  ll40ls start pwm
  ll40ls test pwm
  ll40ls info pwm

When using the Lidar-lite from the servo rail (PWM), make sure it is powered by some ESC/BEC. If the Pixhawk is just connected to the power module or to USB, the rail won't be powered.

LightWare SF02/F Laser Rangefinder (40 m)

The picture below shows the wiring of the SF02/F for a serial port of Pixhawk. With 150 mA maximum current it can be connected to any of the four serial ports.

The pinout has been validated. Note: Pin 10 / COM of the SF02/F is internally connected to pin 2 and does not need to be connected in this setup.

Pixhawk UART pin SF02/F pin Comment
1 / +5V 3 / +5V Power supply
2 / TX 9 / RX 3.3V UART SF02/F receive
3 / RX 8 / TX 3.3V UART SF02/F transmit
6 / GND 2 / - Ground

It is neccessary to check, if the SF02 Laser is set to 9600 baud. Otherwise, PX4 Firmware will not recognize the datastream. To set the correct baud-rate, you have to connect the Laser via USB to the lightware terminal. By pressing the space-bar you get to the settings. Changing parameters has to be done with pressing the corresponding char-keys, to change the values.

To test, if the driver works, it can be started with Tera Term VT:

sf0x start

Then, there is a test routine:

sf0x test

It will create outputs (RAW) similar to this for 0 to 40 meters:

SF02/F Range Finder Setup

To start the sensor in PX4, please add a file called etc/extras.txt to your microSD card with this content:

sf0x start

Plug the SF02/F into TELEM2 or Serial 4/5 of Pixhawk. The wiring of the SF02/F is explained on the Rangefinder page.

MaxBotix I2CXL-MaxSonar-EZ

This series of ultrasonic rangefinders has an I2C interface. Up to 6 sensors are supported on the I2C bus.

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