FreqTest3.ino

/* FreqMeasureMulti - Example with serial output
 * http://www.pjrc.com/teensy/td_libs_FreqMeasure.html
 *
 * This example code is in the public domain.
 * 
 * I connected PIN 4 to PIN 6, PIN 4 to PIN 10 and PIN 3 to PIN 9
 * Results for Serial Output "n, 1463.99,  50.0000000000, 341520.84"
 * 
 * Uncomment line 95 to see last value change
 * 
 * There is some jitter in the 50 Hz signal which may be interupts
 * but more likely just floating point precision
 */
#include <FreqMeasureMulti.h>

// Measure 3 frequencies at the same time! :-)
FreqMeasureMulti freq1;
float engineRPM;

void setup() {
  Serial.begin(57600);
  while (!Serial) ; // wait for Arduino Serial Monitor
  delay(10);
  Serial.println("FreqMeasureMulti Begin");
  delay(10);
  freq1.begin(9);
}

void loop () {
  int count = 6;
  float raw = 0;
  engineRPM = 0;
  for (int i=0; i< count; i++) raw += freq1.read();
  engineRPM = freq1.countToFrequency(raw / count) * 14.28;
  Serial.print("Engine RPM: ");
  Serial.println(engineRPM);
}