Using single chip microcomputer to realize ultrasonic obstacle avoidance car

Creating an ultrasonic obstacle avoidance car using a single-chip microcontroller is a popular embedded systems project. The car uses an ultrasonic sensor to detect obstacles and adjusts its movement accordingly. Below is a step-by-step guide to designing and implementing this project:

1. System Overview
The system consists of:

• Microcontroller: Acts as the brain of the car (e.g., STM32, ESP32, Arduino, or PIC).
• Ultrasonic Sensor: Measures the distance to obstacles (e.g., HC-SR04).
• Motor Driver: Controls the motors for movement (e.g., L298N or TB6612FNG).
• DC Motors: Drive the wheels of the car.
• Power Supply: Provides power to the microcontroller, motors, and sensors.

2. Hardware Components

1. Microcontroller: STM32, ESP32, or Arduino.

2. Ultrasonic Sensor: HC-SR04.

3. Motor Driver: L298N or TB6612FNG.

4. DC Motors: Two or four motors for movement.

5. Chassis: A car chassis with wheels.

6. Power Supply: Batteries (e.g., 9V or 12V) and voltage regulators (e.g., 5V for the microcontroller).

7. Jumper Wires and Breadboard: For connections.

3. Circuit Design

1. Ultrasonic Sensor Connection:

• VCC: Connect to 5V.
• GND: Connect to GND.
• Trig: Connect to a GPIO pin (e.g., PA0).
• Echo: Connect to another GPIO pin (e.g., PA1).

1. Motor Driver Connection:

• IN1, IN2, IN3, IN4: Connect to GPIO pins (e.g., PB0, PB1, PB2, PB3).
• ENA, ENB: Connect to PWM-capable GPIO pins (e.g., PA8, PA9).
• VCC: Connect to the motor power supply (e.g., 9V).
• GND: Connect to GND.
• OUT1, OUT2, OUT3, OUT4: Connect to the DC motors.

1. Power Supply:

• Use a voltage regulator (e.g., LM7805) to provide 5V to the microcontroller and sensors.
• Connect the motor power supply directly to the motor driver.

4. Software Design
Step 1: Initialize Peripherals

• Configure GPIO pins for the ultrasonic sensor and motor driver.
• Set up timers for PWM (to control motor speed).

Step 2: Measure Distance

• Use the ultrasonic sensor to measure the distance to obstacles.
• Send a 10µs pulse to the Trig pin.
• Measure the pulse width on the Echo pin to calculate the distance.

Step 3: Control Motors

• Use the motor driver to control the direction and speed of the motors.
• Implement functions for forward, backward, left, right, and stop movements.

Step 4: Implement Obstacle Avoidance Logic

• If an obstacle is detected within a certain distance (e.g., 20 cm), stop or reverse the car.
• Turn left or right to avoid the obstacle.

5. Example Code (STM32CubeIDE)
Ultrasonic Sensor Code

c

#include "stm32f4xx_hal.h"

#define TRIG_PIN GPIO_PIN_0
#define TRIG_PORT GPIOA
#define ECHO_PIN GPIO_PIN_1
#define ECHO_PORT GPIOA

uint32_t get_distance(void) {
    // Send 10µs pulse to Trig pin
    HAL_GPIO_WritePin(TRIG_PORT, TRIG_PIN, GPIO_PIN_SET);
    HAL_Delay(0.01); // 10µs delay
    HAL_GPIO_WritePin(TRIG_PORT, TRIG_PIN, GPIO_PIN_RESET);

    // Measure pulse width on Echo pin
    uint32_t start_time = 0, end_time = 0;
    while (HAL_GPIO_ReadPin(ECHO_PORT, ECHO_PIN) == GPIO_PIN_RESET);
    start_time = HAL_GetTick();
    while (HAL_GPIO_ReadPin(ECHO_PORT, ECHO_PIN) == GPIO_PIN_SET);
    end_time = HAL_GetTick();

    // Calculate distance (in cm)
    uint32_t pulse_width = end_time - start_time;
    uint32_t distance = pulse_width * 0.034 / 2; // Speed of sound = 340 m/s
    return distance;
}

Motor Control Code

c

void move_forward(void) {
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_0, GPIO_PIN_SET); // IN1
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_1, GPIO_PIN_RESET); // IN2
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_2, GPIO_PIN_SET); // IN3
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, GPIO_PIN_RESET); // IN4
}

void move_backward(void) {
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_0, GPIO_PIN_RESET); // IN1
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_1, GPIO_PIN_SET); // IN2
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_2, GPIO_PIN_RESET); // IN3
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, GPIO_PIN_SET); // IN4
}

void turn_left(void) {
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_0, GPIO_PIN_RESET); // IN1
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_1, GPIO_PIN_SET); // IN2
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_2, GPIO_PIN_SET); // IN3
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, GPIO_PIN_RESET); // IN4
}

void turn_right(void) {
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_0, GPIO_PIN_SET); // IN1
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_1, GPIO_PIN_RESET); // IN2
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_2, GPIO_PIN_RESET); // IN3
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, GPIO_PIN_SET); // IN4
}

void stop(void) {
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_0, GPIO_PIN_RESET); // IN1
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_1, GPIO_PIN_RESET); // IN2
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_2, GPIO_PIN_RESET); // IN3
    HAL_GPIO_WritePin(GPIOB, GPIO_PIN_3, GPIO_PIN_RESET); // IN4
}

Main Code

c

int main(void) {
    HAL_Init();
    SystemClock_Config();
    GPIO_Init();

    while (1) {
        uint32_t distance = get_distance();

        if (distance < 20) { // Obstacle detected
            stop();
            HAL_Delay(500);
            move_backward();
            HAL_Delay(500);
            turn_left();
            HAL_Delay(500);
        } else { // No obstacle
            move_forward();
        }
    }
}

6. Testing and Debugging

1. Test the Ultrasonic Sensor:

Verify that the sensor accurately measures distance.

1. Test Motor Control:

Ensure the motors move in the correct direction and speed.

1. Test Obstacle Avoidance:

Place obstacles in front of the car and verify that it avoids them.

7. Enhancements

1. Add Speed Control:

Use PWM to control motor speed.

1. Add Multiple Sensors:

Use multiple ultrasonic sensors for better obstacle detection.

1. Add Bluetooth/Wi-Fi Control:

Use an ESP32 to add remote control via a smartphone app.

1. Add Display:

Use an LCD or OLED to display distance and status.

By following these steps, you can build an ultrasonic obstacle avoidance car using a single-chip microcontroller.