超音波感測

pulseIn(pin, value)
pulseIn(pin, value, timeout)

Parameters

pin: the number of the pin on which you want to read the pulse. (int)

value: type of pulse to read: either HIGH or LOW. (int)

timeout (optional): the number of microseconds to wait for the pulse to start;
                                default is one second (unsigned long)

Returns

the length of the pulse (in microseconds)
or 0 if no pulse started before the timeout (unsigned long)

unsigned long ul;

void setup() {

  Serial.begin(9600);

}

void loop() {

  Serial.println(sizeof(ul));

  delay(1000);

}

//4 byte 

#define trigPin   7

#define echoPin   8

unsigned long duration;

int distance;

void setup() {

pinMode(trigPin, OUTPUT);

//pinMode(echoPin, INPUT);

Serial.begin(9600);

}

void loop() {

// Clears the trigPin

digitalWrite(trigPin, LOW);

delayMicroseconds(2);

// Sets the trigPin on HIGH state for 10 micro seconds

digitalWrite(trigPin, HIGH);

delayMicroseconds(10);

digitalWrite(trigPin, LOW);

// Reads the echoPin,

//returns the sound wave travel time in microseconds

duration = pulseIn(echoPin, HIGH);

// Calculating the distance

distance= duration*0.034/2;

Serial.print("Distance: ");

Serial.println(distance);

delay(100);

}