RasPiRobot using ESP32

This is a personal project to breathe life into an old Raspberry Pi Rover project using an ESP32 CPU, ROS2 and micro-ROS.

Project structure

The rover is controlled by an ESP32 which is fairly limited, so the ESP32 only controls the rover hardware and communicates with the base station using Wi-Fi. The base station software runs on the PC inside a docker and is used to send commands to the rover and process data received from the rover's sensors. This split was decided on so that the hardware and software can be developed separately.

-----------------------------------------------------------       ----------------------------------------
| Base station                                            |       | Rover                                |
| -----------------    ----------------    -------------- | Wi-Fi | ---------------    ----------------- |
| | ROS processes | <> | ROS Messages | <> | uROS Agent | <======>| | uROS Client | <> | Rover Drivers | |
| -----------------    ----------------    -------------- |       | ---------------    ----------------- |
-----------------------------------------------------------       ----------------------------------------

The project software structure shown above is roughly reflected in the directory structure:

• docker - A docker based on Ubuntu server 20.04LTS that has:
  • The micro-ROS agent.
  • The micro-ROS client. NOTE: The client has to be build in the same workspace as the agent.
  • Basic display X window capabilities for tools such as RQt.
  • Other ROS2 packages needed to control the robot.
• raspi_robot_messages - messages used to communicate between the rover and the base station.
• rover - software for the rover.
  • raspi_rover - the application files for the rover.
  • raspi_robot_driver - driver software for the RasPiRobot board.

RasPi Robot Rover

The RasPi Robot Rover designed to be a flexible platform for testing ideas on. To ensure that the code is easy to modify, the drivers on the rover are deliberately simple and are exposed to the base station so that the software can be rebuilt rapidly without having to rebuild and flash the code for the rover. All rover messages and services are communicated with the base station using Wi-Fi.

The RasPi Robot Rover custom ROS messages and services are defined in the raspi_robot_msgs package.

In addition, the rover will publish some diagnostic messages for debugging purposes.

Done

• The ESP32 docker can be used to build, flash and monitor the ESP32. (3hrs)
• The Base station docker can be used to build the micro-ROS agent and ROS2 tools, e.g. RQt. (4hrs)
• Define custom messages to be used between rover and base station. (2hrs)
• Review stuff in other projects that might be useful for this project. Especially, the 'esp32-raspi-robot' README files. (2hrs)
• Complete rover wiring. (14 hrs).
• Docker-client works for example code. (7hrs)
• Build existing software. The method of building seems to have changed! (14 hrs).
  • Going back to old way of doing things.
    • Add script to install my code and build it.
    • Run test code. Works with micro-ROS agent docker.
• Added battery status message. (8 hrs)
  • Battery monitoring uses voltage divider onto ADC pin.
    • Accuracy: -0.11V from voltmeter, -0.15 from charger, -0.20V from tester.
  • Std msg Int32 being used as BatteryState message causes crash. Issue raised to deal with later.
  • Tested using micro-ROS agent docker.
• Build agent using raspi_robot_msgs. Got back to a working setup. Agent builds and runs. Added raspi_robot_msgs to agent (this took a while, see build_system.md for details).
  • LEDs
    • Implemented. Needs testing from agent. Works.
  • Motors
    • Implemented. Needs testing from agent. Works. 2hrs
• Connect the ESP32 to agent docker and send messages both ways. DONE.
  • Two identical dockers, base stations and rover client. Can I use one? YES. Only one workspace needed. Remove base station docker. DONE. Move client docker and rename. DONE. 30mins.
• Report range. #9 30 minutes.
• Implement cmd_vel to move. #5 1hr.
• Fix RQt. Missing packages? #7
• Implement odom publisher. #6
  • Implement odom publisher publishing fake data. 1hr.
  • Implement encoder driver. Simple driver done. 1hr The driver can generate spurious counts. Added bug.
  • odom to publish position change based on encoder data. Added app_message_files to hold robot specifics and to fill in messages as they were cluttering up the app.c file. Odometry message uses fake data. 3hrs Added timestamp info to header. Not quite working right. 2h00 Added odom publishing info. Data does not look right. 2h00

Total hours: 62

WIP

• Implement odom publisher. #6

  • Test odometry and debug. 4 hours.

• Use encoders to provide feedback for motor control #12 Need to add calculations to convert desired m/s value into encoder ticks per second. 1hr

To do

• Implement each message/service and test.

  • Sonar position #8
    • Add driver for servos. Must support multiple instances.
    • Implement service to set position and report set value. Having problems with servo hardware.
    • Need a servo tester to prove voltages etc. will work for the ESP32. 7h30 so far.

• Implement diagnostic message. #4. This is a pain to make work so have given up on it for now.

  • Add array containing:
    • Robot status.
      • Raw encoder values.
      • Raw motor PWM values.
    • Wi-Fi status.
      • SSID.
      • Signal strength.
      • Connected.

• Make the rover do something interesting!

  • Will need PID controller as the motors have different characteristics.
  • Generate map of route taken.

• Test Arduino style build for ESP32. https://discourse.ros.org/t/micro-ros-porting-to-esp32/16101/13 micro-ROS/micro_ros_espidf_component#9