 
 unsigned long lastmillis;
 
+File file;
+
 void setup() {
   Serial.begin(9600);
 

  }
  
}
void rpm_counter() {
  engine_pulses++;
}

* Could be used alone or with Arduino DataLogger
* Some information about interrupts:
* - http://arduino.cc/en/Reference/attachInterrupt
* About SD Cards:
* - https://learn.adafruit.com/adafruit-micro-sd-breakout-board-card-tutorial/format
* Some useful information about Aprilia RSV/SL bikes work: (See: http://www.aprilia-v60.com/index.php?topic=262315)
* - Speed sensor: purple/green wire=Vcc ~ 9V ? / grey/white: signal ~6.5V, falling to 0V
* - Engine pulses/revolution: 3 if read from the dashboard wire
* - Engine pulses/revolution: 6 if crank shaft sensor is used
* - Wheel pulses/revolution: 5
*/

#include <SPI.h>
#include <SD.h>

#define ENGINE_PULSES_PER_REVOLUTION 3
#define WHEEL_PULSES_PER_REVOLUTION 5
