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INF2004_Project
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INF2004_Project/README.md

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freeRTOS-car

This project is a car that uses the Raspberry Pi Pico and FreeRTOS to move around a maze.

Configurations

All Configurations are in the folder frtos/config, the file frtos/config/car_config.h contains the main configurations for the car.

Build

Configure your Pico SDK and FreeRTOS Kernel Path in your local environment

mkdir build
cd build
cmake ..
make

Flash

cd build
cp freeRTOS-car.uf2 /media/$USER/RPI-RP2

Components

Motors

Motor module consist of 4 components:

  1. motor_init: Initialises the pins and struct stated in motor_config and car_config, and the free rtos tasks related. Call motor_init followed by motor_tasks_init to start.
  2. motor_speed: Monitors the speed of the motors by interrupt. Each falling edge of the wheel encoder will trigger the interrupt and the time elapsed since last trigger will be recorded and thus calculate the speed and distance travelled since boot. Includes functions to adjust the duty cycle of the motor.
  3. motor_pid: PID function to match the right motor duty cycle to the left motor such that the car can move straight, with 50ms interval.
  4. motor_direction: Sets the direction of the motor to control the car using bit masks. Includes functions that work with the magnetometer to turn the car to/by specific yaw.

Ultrasonic Sensor

  1. Ultrasonic sensor package is in frtos/ultrasonic_sensor, and its configuration is in frtos/config/ultrasonic_sensor_config.h. It contains the drivers and FreeRTOS tasks to output and read the ultrasonic sensor data.

  2. ultrasonic_init: Initialises the pins and struct stated in ultrasonic_sensor_config and car_config, and the free rtos tasks related. Call ultrasonic_init followed by ultrasonic_tasks_init to start.

  3. The function check_obstacle() updates one of the parameter in the car's obstruction struct (s_obs_struct) in car_config to tell the car's whether it detects an obstruction .

Line Sensor

Magnetometer

The magnetometer used is the LSM303DLHC from STMicroelectronics.

Magnetometer package is in frtos/magnetometer, and its configuration is in frtos/config/magnetometer_config.h. It contains the drivers and FreeRTOS tasks to read the magnetometer data.

All the magnetometer data (roll, pitch, yaw) calculated is stored in the direction_t struct, which is defined in frtos/config/magnetometer_config.h.

Filtering

The magnetometer initially used a complementary filter (with the accelerometer) to calculate the Yaw, and the temperature, sensor was used to perform an offset correction. But raw data was accurate enough to use it directly.

An initial calibration method for the magnetometer was implemented, with the use of 100 initial samples, and then a bias calculation. This method was not used in the final version, because the raw data was accurate enough.

The final version of the magnetometer uses a moving average filter to smooth the data and a bias of 0 degrees.

Barcode (Line) Sensor

WiFi (Web Server) Module