Calibrate and test a Parallax PING))) Sensor

ping_calibrate.c

#include <Ping.h>

Ping ping = Ping(12, 0, 0);
boolean is_calibrated = false;
float calibration_distance = 0.00;
float current_distance = 0.00;
int alarm_pin = 13;

// because my IO shield is fubar
// and has H/L mixed
#define ON LOW
#define OFF HIGH

void setup() {
  Serial.begin(9600);
  pinMode(alarm_pin, OUTPUT);
}

void loop() {
  if(!is_calibrated) {
    calibration_distance = get_calibration_distance();
    is_calibrated = true;
    Serial.println("PING Calibration Successful");
    Serial.print("PING Distance Set at: ");
    Serial.print(calibration_distance);
    Serial.print(" cm");
    Serial.println();
  }
  
  if(!is_calibrated) {
    Serial.println("PING Failed Calibration Routine");
  }
  
  if(is_calibrated) {
    ping.fire();
    Serial.print("PING Distance: ");
    Serial.print(ping.centimeters());
    Serial.print(" cm");
    Serial.println();
  }
  delay(1000);
  
  /**
    trigger alarm if current measured distance deviates from
    calibrated distance by more than +/- 2.00 cm
    */
  if(is_calibrated) {
    ping.fire();
    current_distance = ping.centimeters();
    
    if((current_distance > calibration_distance + 2.00) || (current_distance < calibration_distance - 2.00)) {
       digitalWrite(alarm_pin, ON);
    } else {
      digitalWrite(alarm_pin, OFF);
    }
  }
}

float get_calibration_distance() {
  // debugging
  float calibration_total = 0.00;
  Serial.print("Calibrating");
  for( int i = 0; i <= 9; i++) {
    ping.fire();
    calibration_total += ping.centimeters();
    // debugging
    Serial.print(" .");
    delay(1000);
  }
  Serial.println(" OK");
  return calibration_total/10.00; // # average distance
}

Could probably add some error checking in the main part of loop() to verify that get_calibration_distance() succeeded before setting is_calibrated to TRUE.

How do I get a copy of the <Ping.h> file.

Thanks.

Givi