const int pwmPin = 11;
const int measurePin = 4;

volatile unsigned long start_time = 0, end_time = 0, delta_time = 0;
int flag_measure = 0;

unsigned long my_pulseIn(unsigned int pin, unsigned int value, unsigned int timeout) {
  if(flag_measure) {
    flag_measure = 0;
    return delta_time;
  }
}

void measure() {
  unsigned int state = digitalRead(measurePin);
  if(state) { // 상승엣지이면 if(state == HIGH)
    start_time = micros();// 시작 시간 측정
  }
  else { // 하강엣지
    end_time = micros();// 끝 시간 측정
    delta_time = end_time - start_time;// 시간 간격 계산: 끝 시각 - 시작 시각
    flag_measure = 1;
  }
}

void setup() {
  Serial.begin(9600);
  pinMode(measurePin, INPUT);
  pinMode(pwmPin, OUTPUT);
  attachInterrupt(digitalPinToInterrupt(measurePin), measure, CHANGE);
  analogWrite(pwmPin, 127);
}

void loop() {
  unsigned long width = my_pulseIn(measurePin, HIGH, 4000); // 펄스너비 읽기
  int out = map(width, 0, 2020, 0, 254); // PWM 범위로 변환
  Serial.print(width);
  Serial.print(".");
  Serial.println(out);
  delay(100);
}