写一个arduino代码,要求是:L298n 驱动小车,如果智能小车左前或者右前的红外线检测到前方距离小于20厘米,就启动舵机云台超声波检查左边90度和右边90度的距离,然后控制小车倒车500毫秒后,向距离大的一边转向,倒车时小车后部左后和右后灯亮，间断蜂鸣，向右转时，右前和右后灯亮，间断蜂鸣，向左转时，左前和左后灯亮，间断蜂鸣

以下是实现您要求的Arduino代码，需要连接L298N、红外线传感器、超声波模块、舵机和LED灯：

#include <Servo.h>

#define trigPin 9
#define echoPin 10
#define rightIR A0
#define leftIR A1
#define enA 5
#define in1 6
#define in2 7
#define enB 11
#define in3 12
#define in4 13
#define leftLED 3
#define rightLED 4
#define buzzer 8

int distanceLeft = 0;
int distanceRight = 0;
int distance = 0;
int speed = 200;
Servo servo;
int angle = 90;

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(rightIR, INPUT);
  pinMode(leftIR, INPUT);
  pinMode(enA, OUTPUT);
  pinMode(in1, OUTPUT);
  pinMode(in2, OUTPUT);
  pinMode(enB, OUTPUT);
  pinMode(in3, OUTPUT);
  pinMode(in4, OUTPUT);
  pinMode(leftLED, OUTPUT);
  pinMode(rightLED, OUTPUT);
  pinMode(buzzer, OUTPUT);
  servo.attach(2);
}

void loop() {
  // 红外线检测
  int leftDistance = analogRead(leftIR);
  int rightDistance = analogRead(rightIR);
  if (leftDistance < 20 || rightDistance < 20) {
    // 舵机旋转
    servo.write(0);
    delay(500);
    distanceLeft = getDistance(180);
    servo.write(180);
    delay(500);
    distanceRight = getDistance(0);
    // 判断转向
    if (distanceLeft > distanceRight) {
      // 向左转
      digitalWrite(in1, LOW);
      digitalWrite(in2, HIGH);
      digitalWrite(in3, HIGH);
      digitalWrite(in4, LOW);
      digitalWrite(leftLED, HIGH);
      digitalWrite(rightLED, LOW);
      tone(buzzer, 1000, 200);
    } else {
      // 向右转
      digitalWrite(in1, HIGH);
      digitalWrite(in2, LOW);
      digitalWrite(in3, LOW);
      digitalWrite(in4, HIGH);
      digitalWrite(leftLED, LOW);
      digitalWrite(rightLED, HIGH);
      tone(buzzer, 2000, 200);
    }
    // 倒车
    analogWrite(enA, speed);
    analogWrite(enB, speed);
    digitalWrite(leftLED, HIGH);
    digitalWrite(rightLED, HIGH);
    delay(500);
    analogWrite(enA, 0);
    analogWrite(enB, 0);
    digitalWrite(leftLED, LOW);
    digitalWrite(rightLED, LOW);
  } else {
    // 直行
    digitalWrite(in1, HIGH);
    digitalWrite(in2, LOW);
    digitalWrite(in3, HIGH);
    digitalWrite(in4, LOW);
    digitalWrite(leftLED, LOW);
    digitalWrite(rightLED, LOW);
    noTone(buzzer);
    analogWrite(enA, speed);
    analogWrite(enB, speed);
  }
}

int getDistance(int angle) {
  // 超声波检测
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  distance = pulseIn(echoPin, HIGH) / 58.0;
  servo.write(angle);
  return distance;
}

代码中的注释可以帮助您理解代码的功能。请注意，代码中的舵机引脚为2，您需要根据自己的连接情况修改。代码中的速度为200，您可以根据需要进行调整。