#define ECHO_PIN 2
#define TRIG_PIN 3
#include <stdio.h>
#include <math.h>

void setup() {
  Serial.begin(115200);
  pinMode(LED_BUILTIN, OUTPUT);
  pinMode(TRIG_PIN, OUTPUT);
  pinMode(ECHO_PIN, INPUT);
  //A4988引脚接线
  pinMode(8, OUTPUT);//右侧转向，0=逆时针，1=顺时针
  pinMode(9, OUTPUT);
  pinMode(10, OUTPUT);//左侧转向，0=逆时针，1=顺时针
  pinMode(11, OUTPUT);
}

float readDistanceCM() {
  digitalWrite(TRIG_PIN, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG_PIN, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG_PIN, LOW);
  int duration = pulseIn(ECHO_PIN, HIGH);
  return duration * 0.034 / 2;
}

  long i = 0;

void loop() {
  //超声波
  float distance = readDistanceCM();
  bool isNearby = distance < 50;
  digitalWrite(LED_BUILTIN, isNearby);
  Serial.print("Measured distance: ");
  Serial.println(readDistanceCM());
  Serial.println( i );
  delay(1);

  //电机控制
  bool run = isNearby ;

  if ( 0==run ) {  //前进
    if ( i != 0 ){
      double runResult = 50 / (2.1352 * cos( i * 1.475 ));
      int b = runResult + 10 ;
      for ( ;b != 0 ; b--){
        digitalWrite(8,1) ;  digitalWrite(10,0);//前进
        delay(10);
        digitalWrite(9,LOW) ;  digitalWrite(11,HIGH);
        delay(10);
        digitalWrite(11,LOW) ;  digitalWrite(9,HIGH);
      }
    }
    else{
     digitalWrite(8,1) ;  digitalWrite(10,0);//前进
     delay(10);
     digitalWrite(9,LOW) ;  digitalWrite(11,HIGH);
     delay(10);
     digitalWrite(11,LOW) ;  digitalWrite(9,HIGH);};

    for ( ; i != 0 ; i--)//检测是否旋转过
        {
          float distance = readDistanceCM();
          bool isNearby = distance < 50;
          Serial.print("Measured distance: ");
          Serial.println(readDistanceCM());
          Serial.println( i );
          delay(1);
          digitalWrite(8,LOW) ;  digitalWrite(10,LOW);//左转
          delay(10);digitalWrite(9,LOW) ; delay(10); digitalWrite(9,HIGH);//2步
          delay(10);digitalWrite(11,LOW) ; delay(10); digitalWrite(11,HIGH);
        };
  }
  else //转向
  {
    if ( run ) {
      digitalWrite(8,HIGH) ;  digitalWrite(10,HIGH);//左转
      delay(10);digitalWrite(9,LOW) ; delay(10); digitalWrite(9,HIGH);//2步，约转向1.5度
      delay(10);digitalWrite(11,LOW) ; delay(10); digitalWrite(11,HIGH);
      i++;
    }
    else ;
  }; 

};