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Ultrasonic Distance Sensor: Try a different strategy with pulseIn() #1

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Ultrasonic Distance Sensor: Try a different strategy with pulseIn() #1

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39 changes: 26 additions & 13 deletions Tutorials/Ultrasonic Distance Sensor/README.md
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Expand Up @@ -26,28 +26,41 @@ This method is what is most widely used when starting out. It relies on **delayM
Below is some starting code, which will allow you to read the distance in centimeters.

```C++
int pingPin = 6;
int echoPin = 7;
int triggerPin = 12;
int echoPin = 11;
int cm;
int missedPulses = 0;

void setup() {
Serial.begin(9600);
pinMode(6, OUTPUT);
pinMode(7, INPUT);
pinMode(triggerPin, OUTPUT);
pinMode(echoPin, INPUT);
}

void loop() {
//additional 2 microsecond delay to ensure pulse clarity
digitalWrite(pingPin, LOW);
// additional 2 microsecond delay to ensure pulse clarity
digitalWrite(triggerPin, LOW);
delayMicroseconds(2);
digitalWrite(pingPin, HIGH);
digitalWrite(triggerPin, HIGH);
delayMicroseconds(10);
digitalWrite(pingPin, LOW);
digitalWrite(triggerPin, LOW);

// pulseIn waits for echo to go from HIGH to LOW
long duration = pulseIn(echoPin, HIGH, 11600);

if (duration != 0) {
// echo received, convert time it took to centimeters
// sound travels 29cm per microsecond, back-and-forth
cm = duration / 29 / 2;
missedPulses = 0;
} else {
if (missedPulses < 5) {
missedPulses++;
} else {
cm = 0;
}
}

//pulseIn waits for signal to go from HIGH to LOW, default timeout is 1000000
unsigned long duration = pulseIn(echoPin, HIGH);
//since sound travels roughly 29cm per microsecond we divide by 29
//then again by 2 since the duration of the signal was equal to the sound traveling outward and back
int cm = duration / 29 / 2;
Serial.println(cm);
}
```
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