windspeed.cpp

#include "windspeed.h"

/**
 * Interrupt Service Routine to run when a hall effect sensor triggers a rising interrupt
 */
void windspeed_isr(void)
{
  windspeed_revs++;
}

/**
 *  Returns the average rpm since the last call to get_windspeed_avg_rpm
 */
float get_windspeed_avg_rpm()
{
  unsigned long now = millis();
  unsigned long elapsed = now - windspeed_last;
  float rpm = (float) windspeed_revs / (float) elapsed * 60000;
  windspeed_last = now;
  windspeed_revs = 0;
  return rpm;
}

windspeed.h

#ifndef _WINDSPEED_H_
#define _WINDSPEED_H_

unsigned long windspeed_last = 0;
unsigned int windspeed_revs = 0;

void windspeed_isr(void);
void get_windspeed_avg_rpm();

#endif /** _WINDSPEED_H_ include guard **/