2.12/2.120 Intro to Robotics
Spring 2024¹

We have already written most of the code for this lab. We hope that you will use the extra free time to fully understand the mobile robot codebase and prepare for the final competition. Have a great spring break!

Take some time to understand robot_main.cpp, robot_drive.cpp, robot_motion_control.cpp, and robot_wireless.cpp. At a high level:

• robot_main.cpp: Includes the setup() and loop() functions, telling the microcontroller exactly what to do and when.
• robot_drive.cpp: Sets up the motors and implements a PI controller to follow velocity setpoints.
• robot_motion_control.cpp: Calculates odometry and setpoints based on either joystick or a given trajectory.
• robot_wireless.cpp: Sets up two-way wireless communication with and sends messages to the microcontroller on your controller.

Open robot_motion_control.cpp and read through updateOdometry(). Make sure that you understand exactly how this function calculates odometry data. For reference:

Make sure your PlatformIO environment is set to be env:robot and upload the code to the microcontroller on your mobile robot. Once the code has finished uploading, unplug the robot from your computer, set it on the ground, power it on, and press RST. Your robot should now autonomously follow a U-Turn!

Your U-Turn will probably not be perfect! While odometry is straightforward to implement, it suffers from problems such as position drift due to wheel slippage. IMU data (or some combination of IMU and odometry) will likely be more reliable.

In robot_motion_control.cpp, comment out #define UTURN and uncomment #define CIRCLE. This will change the followTrajectory() function to follow a circle instead of a U-Turn. Your robot should now autonomously follow a circle!

In order to establish wireless communication, we first have to make sure that both microcontrollers know each other's MAC addresses.

Run lib/Wireless/examples/get_mac.cpp (you will have to temporarily move the existing files inside the src/robot/ folder and replace them with get_mac.cpp). Open lib/Wireless/wireless.h and change robotAddr to the MAC address being printed to the Serial monitor.

Connect to the microcontroller on your controller and change your PlatformIO environment to be env:controller.

Run lib/Wireless/examples/get_mac.cpp (you will have to temporarily move the existing files inside the src/controller/ folder and replace them with get_mac.cpp). Open lib/Wireless/wireless.h and change controllerAddr to this MAC address.

Run src/test_controller/controller_test.cpp. You should see joystick readings being printed to your Serial monitor.

Upload controller_main.cpp and controller_wireless.cpp to the microcontroller on your controller. This will read the joystick and set up two-way wireless communication with the microcontroller on the mobile robot.

In robot_motion_control.cpp, comment out #define CIRCLE and uncomment #define JOYSTICK. This will change the followTrajectory() function to follow a joystick instead of a circle.

Set your PlatformIO environment back to env:robot. Upload robot_main.cpp, robot_drive.cpp, robot_motion_control.cpp, and robot_wireless.cpp to the microcontroller on your mobile robot. At this point, you should be able to drive your mobile robot around with your joystick!

In robot_motion_control.cpp, comment out #define JOYSTICK and uncomment #define YOUR_TRAJECTORY. In the followTrajectory() function, make your own path using a state machine, taking UTURN as inspiration.

Before you leave, please fill out https://tinyurl.com/212-feedback.

Integrate the IMU with your mobile robot! This will probably be very useful for your final project.

Replace the existing wheels with mecanum wheels! Mecanum wheels allow the robot to move in any direction. However, the odometry and controller will be slightly different.