从Arduino中的超声波传感器获取以英寸和厘米为单位的距离

我正在修补一个简单的Arduino草图，它使用超声波传感器检测距离。据我所知，扳机发出“砰”的一声。回声监听返回计算距离的回声。这是以微秒为单位测量的

如果这是正确的，那么问题是，如何从该ping（以微秒为单位）确定英寸和厘米？这只是一个基本的数学/物理，还有一个基本的公式吗

void loop() {
 digitalWrite(trigPin, LOW); 
 delayMicroseconds(2); 
 digitalWrite(trigPin, HIGH);
 delayMicroseconds(10); 
 digitalWrite(trigPin, LOW);

 duration = pulseIn(echoPin, HIGH);

这是我遇到问题的部分。我想将ping时间从微秒除以英寸，然后再除以厘米：

 distance_in = duration ????;
 distance_cm = duration ????;

 Serial.print(distance_in);
 Serial.print(" in, ");
 Serial.print(distance_cm);
 Serial.print(" cm");
 Serial.println();
 delay(1500);
}

任何帮助，尽可能多的解释将不胜感激。我是Arduino的新手（在数学方面不是举重运动员）

声音以每秒343米的速度传播，这意味着每厘米需要29.155微秒。因此，我们必须将持续时间除以29，然后再除以2，因为声音必须传播两次距离。它移动到对象，然后返回到传感器

---

1cm=0393701在《阿杜伊诺》中，我找到的关于这个主题的最好的文章

---

这是有道理的。非常感谢。

distance_cm = ( duration / 29 ) / 2;
distance_in = distance_cm * 0,393701;    

/* Ping))) Sensor

   This sketch reads a PING))) ultrasonic rangefinder and returns the
   distance to the closest object in range. To do this, it sends a pulse
   to the sensor to initiate a reading, then listens for a pulse
   to return.  The length of the returning pulse is proportional to
   the distance of the object from the sensor.

   The circuit:
    * +V connection of the PING))) attached to +5V
    * GND connection of the PING))) attached to ground
    * SIG connection of the PING))) attached to digital pin 7

   http://www.arduino.cc/en/Tutorial/Ping

   created 3 Nov 2008
   by David A. Mellis
   modified 30 Aug 2011
   by Tom Igoe

   This example code is in the public domain.

 */

// this constant won't change.  It's the pin number
// of the sensor's output:
const int pingPin = 7;

void setup() {
  // initialize serial communication:
  Serial.begin(9600);
}

void loop() {
  // establish variables for duration of the ping,
  // and the distance result in inches and centimeters:
  long duration, inches, cm;

  // The PING))) is triggered by a HIGH pulse of 2 or more microseconds.
  // Give a short LOW pulse beforehand to ensure a clean HIGH pulse:
  pinMode(pingPin, OUTPUT);
  digitalWrite(pingPin, LOW);
  delayMicroseconds(2);
  digitalWrite(pingPin, HIGH);
  delayMicroseconds(5);
  digitalWrite(pingPin, LOW);

  // The same pin is used to read the signal from the PING))): a HIGH
  // pulse whose duration is the time (in microseconds) from the sending
  // of the ping to the reception of its echo off of an object.
  pinMode(pingPin, INPUT);
  duration = pulseIn(pingPin, HIGH);

  // convert the time into a distance
  inches = microsecondsToInches(duration);
  cm = microsecondsToCentimeters(duration);

  Serial.print(inches);
  Serial.print("in, ");
  Serial.print(cm);
  Serial.print("cm");
  Serial.println();

  delay(100);
}

long microsecondsToInches(long microseconds) {
  // According to Parallax's datasheet for the PING))), there are
  // 73.746 microseconds per inch (i.e. sound travels at 1130 feet per
  // second).  This gives the distance travelled by the ping, outbound
  // and return, so we divide by 2 to get the distance of the obstacle.
  // See: http://www.parallax.com/dl/docs/prod/acc/28015-PING-v1.3.pdf
  return microseconds / 74 / 2;
}

long microsecondsToCentimeters(long microseconds) {
  // The speed of sound is 340 m/s or 29 microseconds per centimeter.
  // The ping travels out and back, so to find the distance of the
  // object we take half of the distance travelled.
  return microseconds / 29 / 2;
}