Obstacle Avoiding Car - README

Introduction

This project implements an Obstacle Avoiding Car using the STM32-F401RE microcontroller and Ultrasonic Sensor (HC-SR04) for obstacle detection. The car can be remotely controlled using a Bluetooth module (DX-BT24-A) to move forward, backward, left, or right. If an obstacle is detected within a predefined distance, the car will stop to avoid a collision.

Key Features:

• Remote control via Bluetooth using a mobile phone.
• Obstacle detection using an ultrasonic sensor.
• Movement control with forward, backward, left, and right commands.
• Automatic stop if an obstacle is detected in the path.

Hardware Requirements

• STM32-F401RE Nucleo Board (or any STM32 board with compatible pins).
• Ultrasonic Sensor (HC-SR04) for obstacle detection.
• Bluetooth Module (DX-BT24-A or similar) for wireless communication (UART).
• Motor Driver (e.g., L298N or any suitable driver for controlling the motors).
• DC Motors for movement of the car.
• Buck Converter for converting from 12V to 5V for MCU and other components.
• Jumper wires and a power source (battery or external power supply).
• Any Size Breadboards.

Pin Connections

Component	Pin on ST32-F401RE
Ultrasonic Sensor Trigger	D9
Ultrasonic Sensor Echo	D10
Bluetooth TX	D8
Bluetooth RX	D2
Motor Driver 1 IN1	D3
Motor Driver 1 IN2	D4
Motor Driver 1 IN3	D5
Motor Driver 1 IN4	D6
Motor Driver 2 IN1	D7
Motor Driver 2 IN2	D11
Motor Driver 2 IN3	D12
Motor Driver 2 IN4	D13

Software Requirements

• mbed OS: The code is written using the mbed OS environment and uses mbed libraries for GPIO, serial communication, and timers.
• IDE: You can use the Mbed Studio or the Online Compiler to compile and upload the code to the STM32-F401RE.

Project Overview

This project is designed to allow the car to:

1. Receive movement commands (F, B, L, R, S) via Bluetooth.
2. Detect obstacles in its path using an ultrasonic sensor.
3. Stop the car if an obstacle is detected to prevent a collision.

Bluetooth Communication:

The car can be controlled using a Bluetooth terminal app on your mobile phone. The available movement commands are:

• 'F': Move forward.
• 'B': Move backward.
• 'L': Turn left.
• 'R': Turn right.
• 'S': Stop.

Obstacle Detection:

• The ultrasonic sensor is used to measure the distance to the nearest object in front of the car.
• If the object is within a defined threshold (40 cm), the car will stop moving and print an alert via Bluetooth.
• Note momentum and delays are a factor so it won't stop at 40 cm.

Motor Control:

The motor driver controls the DC motors based on the received Bluetooth commands:

• Forward (F): Both motors rotate forward.
• Backward (B): Both motors rotate backward.
• Left (L): Left motor rotates in reverse while the right motor moves forward.
• Right (R): Right motor rotates in reverse while the left motor moves forward.
• Stop (S): Both motors stop.

How It Works

1. Bluetooth Communication: The car waits for Bluetooth commands to control the movement. The Bluetooth module (HC-05) receives data from a mobile app and sends it to the STM32 board.
2. Obstacle Detection: The ultrasonic sensor sends a pulse, and the board measures the time it takes for the echo to return. The distance is calculated and compared to a threshold (40 cm).
3. Movement Control: Based on the received command, the car moves accordingly. If an obstacle is detected, the movement is halted, and an alert is sent via Bluetooth.

Code Flow

1. bluetooth_communication(): This function reads Bluetooth commands to control the movement (F, B, L, R, S).
2. detect_obstacle(): This function measures the distance to any obstacle in the path. If the distance is less than 40 cm, the obstacle_detected flag is set to true.
3. movement_control(): This function controls the motors based on the received command, stopping the car if an obstacle is detected.
4. send_alert(): Sends a message to the Bluetooth terminal to inform the user of the car's current state (e.g., moving forward, moving backward, obstacle detected).

How to Use

1. Set Up Hardware:
   • Connect the ultrasonic sensor, Bluetooth module, and motor driver as described in the Pin Connections section.
   • Ensure your car’s motors are connected to the motor driver correctly.
   • Power the system using a battery or power supply suitable for the STM32 and motors.

2. Upload the Code:

   • Open the code in the Mbed Studio or Mbed Online Compiler.
   • Select the STM32F401RE board as the target.
   • Compile and upload the code to the STM32 board.

3. Control the Car:

   • Pair your mobile phone with the Bluetooth module (DX-BT24-A).
   • Open a Bluetooth terminal app and send one of the following commands:
     • F to move forward.
     • B to move backward.
     • L to turn left.
     • R to turn right.
     • S to stop the car.
   • The car will move accordingly. If an obstacle is detected, it will stop and send an alert message via Bluetooth.

Troubleshooting

• Car not responding: Ensure that the Bluetooth module is correctly paired with your mobile phone and that the mobile app is sending the correct commands.
• Obstacle detection issues: Check the wiring of the ultrasonic sensor, ensuring that the trigger and echo pins are correctly connected. Also, ensure that there is nothing blocking the sensor’s line of sight.
• Motor not working: Verify the motor driver connections, the motor power supply, and the motor driver logic.

Conclusion

This obstacle avoiding car project demonstrates the integration of a variety of components including Bluetooth communication, ultrasonic sensors, and motor drivers to create an autonomous vehicle capable of avoiding obstacles.