#define keyin 2
// defines variables

const int Trig_Pins = 13;//trig 腳位
const int Echo_Pins = 12;// echo 腳位

bool flag=0;
static long count=0;

float get_distance(int trig, int echo){  //計算距離
  float duration;
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);            //給予trig 10us TTL pulse,讓模組發射聲波
  digitalWrite(trig, LOW);
  duration = pulseIn(echo, HIGH, 5000000);//紀錄echo電位從high到low的時間，就是超音波來回的時間，若5秒內沒收到超音波則回傳0
  return duration / 29 / 2;         // 聲速340m/s ，換算後約每29微秒走一公分，超音波來回所以再除2
}

void setup() 
{
 pinMode(keyin, INPUT);
 pinMode(Trig_Pins, OUTPUT);
 pinMode(Echo_Pins, INPUT);
 Serial.begin(9600); // // Serial Communication is starting with 9600 of baudrate speed

 attachInterrupt(digitalPinToInterrupt(keyin), keytrans, FALLING); //mode= falling edge status
}
void keytrans()
{
 flag=1; //set flag=1
 count++;
}
void loop()
{
 if(flag==1)
 {
 if(digitalRead(keyin) == LOW) //check pin2 status
 {
 delay(80); //delay 80ms
 if(digitalRead(keyin) == LOW) //check pin2 again
 {

 float result= get_distance( Trig_Pins, Echo_Pins);
    Serial.print("Distance: ");
    Serial.print(result);
    Serial.println("cm");
    delay(1000);
 flag=0; //clear flag
 }
 }
 }
}