写一个基于51单片机二驱循迹小车pwm调速代码

好的，这是一个基于51单片机的二驱循迹小车PWM调速代码示例：

#include <reg51.h>

// 定义左右电机驱动引脚
sbit LEFT_MOTOR_PIN1 = P2^0;
sbit LEFT_MOTOR_PIN2 = P2^1;
sbit RIGHT_MOTOR_PIN1 = P2^2;
sbit RIGHT_MOTOR_PIN2 = P2^3;

// 定义左右电机PWM控制引脚
sbit LEFT_MOTOR_PWM = P1^2;
sbit RIGHT_MOTOR_PWM = P1^3;

// 定义循迹传感器引脚
sbit SENSOR_PIN1 = P0^0;
sbit SENSOR_PIN2 = P0^1;
sbit SENSOR_PIN3 = P0^2;
sbit SENSOR_PIN4 = P0^3;
sbit SENSOR_PIN5 = P0^4;

// 定义调速变量
unsigned char leftSpeed = 0;
unsigned char rightSpeed = 0;

void main() {
  // 初始化定时器0
  TMOD |= 0x01;
  TH0 = 0xFC;
  TL0 = 0x67;
  ET0 = 1;
  TR0 = 1;
  EA = 1;

  // 初始化串口
  SCON = 0x50;
  TMOD |= 0x20;
  TH1 = 0xFD;
  TL1 = 0xFD;
  ES = 1;
  TR1 = 1;

  // 无限循环
  while (1) {
    // 读取循迹传感器数据
    unsigned char sensor1 = SENSOR_PIN1;
    unsigned char sensor2 = SENSOR_PIN2;
    unsigned char sensor3 = SENSOR_PIN3;
    unsigned char sensor4 = SENSOR_PIN4;
    unsigned char sensor5 = SENSOR_PIN5;

    // 计算偏差值
    int error = sensor1 * 1 + sensor2 * 2 + sensor3 * 3 + sensor4 * 2 + sensor5 * 1 - 10;

    // 根据偏差值调整左右电机PWM占空比
    leftSpeed = 100 - error * 2;
    rightSpeed = 100 + error * 2;

    // 限制PWM占空比范围
    leftSpeed = leftSpeed > 100 ? 100 : leftSpeed;
    rightSpeed = rightSpeed > 100 ? 100 : rightSpeed;

    // 控制电机转速
    TH1 = leftSpeed;
    TL1 = leftSpeed;
    LEFT_MOTOR_PWM = 1;
    TH1 = rightSpeed;
    TL1 = rightSpeed;
    RIGHT_MOTOR_PWM = 1;

    // 控制电机方向
    if (leftSpeed > 0) {
      LEFT_MOTOR_PIN1 = 1;
      LEFT_MOTOR_PIN2 = 0;
    } else {
      LEFT_MOTOR_PIN1 = 0;
      LEFT_MOTOR_PIN2 = 1;
    }

    if (rightSpeed > 0) {
      RIGHT_MOTOR_PIN1 = 1;
      RIGHT_MOTOR_PIN2 = 0;
    } else {
      RIGHT_MOTOR_PIN1 = 0;
      RIGHT_MOTOR_PIN2 = 1;
    }
  }
}

// 定时器0中断服务程序
void timer0_isr() interrupt 1 {
  TH0 = 0xFC;
  TL0 = 0x67;
  P1 = 0x00;
}

// 串口中断服务程序
void serial_isr() interrupt 4 {
  if (RI) {
    RI = 0;
  }
  if (TI) {
    TI = 0;
  }
}

该代码中使用了定时器0和串口进行PWM输出和调试信息输出，实现了小车的循迹行驶。同时，还对PWM占空比范围进行了限制，并控制电机的转速和方向。最后，通过串口打印调试信息，方便调试和优化程序。