Custom Hardware Driver

In this exercise, we are going to replace our fake_sonar_driver package with the real hardware. To get started, you are provided with a sonar_driver template that implements core communication between the driver node and the hardware. Your task is to complete the given base code with the missing pieces and integrate the driver with ROS.

Motivation

The majority of the work will be done in sonar_hardware_client_node.cpp file, where driver communication takes place. The structure of this node is a bit unconventional: instead of everyting defined in main we create a custom Class that implemets the hardware communication functionalities. This “Class based” approach is actually very common in industrial applications where many different libraries are integrated to a single application.

Hardware

Our device consists of:

  • Arduino Nano v3
  • Pololu AltIMU-10v4
  • Ultrasound sensor HC-SR04

Get the base package for the sonar_driver

  1. Update the ros_training repository located in your home folder:

    cd ~/ros_training
git pull

  2. Copy the sonar_driver package to your catkin_ws workspace:

    cp -r ~/ros_training/resources/sonar_driver ~/catkin_ws/src/

  3. Find and fix the bug deliberately left in the package.

Complete our broken driver code by filling in the missing parts

This work will be combining the knowledge you learned from the past 2 days. Our motivation is to encourage you to work through the familiar problems in a new perspective. For that there will be no detailed step-by-step guide in this assignment.

Once you got the package compiling, open the sonar_hardware_client_node.cpp. Follow the TODO: labels in the code to complete the following tasks:

  1. TODO: Get the following parameters from ROS parameter server:

    Parameter Default value
    serial/port dev/ttyUSB0
    serial/baudrate 115200
    imu/frame_id map

  2. TODO: Set up the following publishers and services:

    Publisher name Datatype topic
    imu_publisher sensor_msgs::Imu imu
    sonar_publisher sensor_msgs::Range sonar_distance
    range_imu_publisher sonar_driver::RangeImu range_imu_combined
    Service name Datatype topic
    set_sonar_range_server sonar_driver::SetSonarRange set_sonar_range
    • Create a custom message for range_imu_publisher that combines sensor_msgs/Range and sensor_msgs/Imu.

  3. TODO: Create a timer to periodically read data from the serial buffer:

    • set the period to 0.05 s (20 Hz)
    • set the callback function to SonarHardwareClient::read

  4. TODO: Clamp the sonar range value between 0 and 2.

  5. TODO: Implement the function for processing the sonar data:

    • Create and publish IMU data as sensor_msgs::Imu message
    • Create and publish sonar data as sensor_msgs::Range message
    • Create and publish our custom sonar_driver::RangeImu message