Project 21.1 超音波測距モジュール／Ultrasonic Ranging

/**********************************************************************
  Filename    : Ultrasonic Ranging
  Description : Use the ultrasonic module to measure the distance.
  Auther      : www.freenove.com
  Modification: 2022/10/25
**********************************************************************/
#define trigPin 13 // define TrigPin
#define echoPin 14 // define EchoPin.
#define MAX_DISTANCE 700 // Maximum sensor distance is rated at 400-500cm.
//timeOut= 2*MAX_DISTANCE /100 /340 *1000000 = MAX_DISTANCE*58.8
float timeOut = MAX_DISTANCE * 60; 
int soundVelocity = 340; // define sound speed=340m/s

void setup() {
  pinMode(trigPin,OUTPUT);// set trigPin to output mode
  pinMode(echoPin,INPUT); // set echoPin to input mode
  Serial.begin(115200);   // Open serial monitor at 115200 baud to see ping results.
}

void loop() {
  delay(100); // Wait 100ms between pings (about 20 pings/sec). 
  Serial.printf("Distance: ");
  Serial.print(getSonar()); // Send ping, get distance in cm and print result 
  Serial.println("cm");
}

float getSonar() {
  unsigned long pingTime;
  float distance;
  // make trigPin output high level lasting for 10μs to triger HC_SR04
  digitalWrite(trigPin, HIGH); 
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  // Wait HC-SR04 returning to the high level and measure out this waitting time
  pingTime = pulseIn(echoPin, HIGH, timeOut); 
  // calculate the distance according to the time
  distance = (float)pingTime * soundVelocity / 2 / 10000; 
  return distance; // return the distance value
}