Using your Time-of-flight Sensor

In this part of the project, you will learn how to estimate the drone’s height using its time-of-flight sensor. The drone is equipped with a VL53L0X, which is used for estimating the distance from the drone to the ground-plane. The sensor outputs a digital signal containing the distance from the sensor and read in by the Raspberry Pi via the GPIO pin using the associated Python library. The voltage value corresponds to distance, but we are going to need to do some work to convert it to real-world units.

Setup

Change to ~/catkin_ws/src on your drone, and then run

git clone https://github.com/h2r/project-sensors-implementation-yourGithubName

You should create a GitHub personal access token for your drone to make this possible. It only needs permissions to read and write to repositories.

Change directories into ~/catkin_ws/src/project-sensors-implementation-yourGithubName. You can run

rosrun project-sensors-yourGithubName student_tof_pub.py  

You may stop student_tof_pub.py with ctrl-c, edit it within that tab, and then re-run

rosrun project-sensors-yourGithubName student_tof_pub.py

to test your changes.

Problem 1: Publish your TOF Reading

In student_tof_pub.py, fill in the minimum range, maximum range, and current range read from the sensor into the ROS message. When you run this node, you will be publishing a ROS Range message which is a standard message included with ROS.

Checkoff:

Using rostopic echo /pidrone/range or the height graph on the web interface, verify that:

• The TOF node is publishing a message with all the fields you want

• The range field of the message is a roughly accurate measure of the drone’s altitude

You can now fly your drone with your own range node!