13_PCINT_ultrasonic(timer1함수를 이용한 거리측정)

#include <PinChangeInterrupt.h>
#include <TimerOne.h>

const int trig_pin = 9;
const int echo_pin = 10;
unsigned long echo_duration =0;
void echoIsr(void) {
  static unsigned long echo_begin = 0;
  static unsigned long echo_end = 0; 
  unsigned int echo_pin_state = digitalRead(echo_pin);
  if (echo_pin_state == HIGH) {
    echo_begin = micros();
  } else {
    echo_end = micros();
    echo_duration = echo_end - echo_begin;

  }
}
void timerIsr(void) {
  if (echo_duration == 0) {
    digitalWrite(trig_pin,LOW);
    delayMicroseconds(2);
    digitalWrite(trig_pin,HIGH);
    delayMicroseconds(2);
    digitalWrite(trig_pin,LOW);
  }  else {
    unsigned long distance = echo_duration / 58;
    Serial.print(distance);
    Serial.println(" cm");
    echo_duration = 0;
  }
}

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  pinMode(trig_pin,OUTPUT);
  pinMode(echo_pin,INPUT);
  Timer1.initialize(500000);
  Timer1.attachInterrupt(timerIsr);
  attachPCINT(digitalPinToPCINT(echo_pin),echoIsr,CHANGE);
}

void loop() {
  // put your main code here, to run repeatedly:
}