#include <LiquidCrystal.h>
#define trigpin 3
#define echopin 2
#define buzzer 11

const int rs = 4, en = 6, d4 = 7, d5 = 8, d6 = 9, d7 = 10;
LiquidCrystal lcd(rs,en,d4,d5,d6,d7);
float distance , temp;

void setup() {
  // put your setup code here, to run once:
  // 这部分是LCD的功能初始化
  pinMode(5, OUTPUT);
  digitalWrite(5, LOW);
  lcd.begin(16,2);

  Serial.begin(115200);
  pinMode(trigpin, OUTPUT);
  pinMode(echopin, INPUT);
  pinMode(buzzer, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  // 初始化HC-SRO04
  digitalWrite(trigpin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigpin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigpin, LOW);

  // 计算结果
  temp = float(pulseIn(echopin, HIGH));
  distance = (temp*17)/1000;

  if( distance <= 60)
  {
    if(distance <= 30)
    {
      tone(buzzer,2200);
    }
    else
    {
      float val = (distance - 30)*20;
      tone(buzzer,2000);
      delay(200);
      noTone(buzzer);
      delay(val);

    }
  }
  else{ // 这部分是大于6-
    noTone(buzzer);
    
  }

  // 串口打印出结果
  Serial.print("探头距离障碍物为：");
  Serial.print(distance);
  Serial.println("cm");

  // 在LCD显示
  lcd.setCursor(0,0);
  lcd.print("distance:");
  lcd.print(distance);
  lcd.println("cm");

  delay(100);
}