/*
AtoD for Seismometer - mimics SEP UK interface
12 Aug 2015 created (without averaging)
*/


//the setup routine runs once when you press reset:


void setup() {

  // initialize serial ommunication at 9600 bits per second:

   Serial.begin(9600);



   //set timer1 interrupt at 20Hz
  
   TCCR1A = 0;  // set entire TCCR1A register to 0
 
  TCCR1B = 0;  // same for TCCR1B
 
  TCNT1  = 0;  //initialize counter value to 0


   //Send samples every 6 Hz (typical seismograph)
 
  OCR1A = 2603;
   // turn on CTC mode
  
   TCCR1B |= (1 << WGM12);
  
   // Set CS10 and CS12 bits for 1024 prescaler

  TCCR1B |= (1 << CS12) | (1 << CS10); 
 
  // enable timer compare interrupt

  TIMSK1 |= (1 << OCIE1A);

 
  sei();//allow interrupts

   }


ISR(TIMER1_COMPA_vect){  // Timer1's interrupt

 
   // send the output to the com port every interrupt
  
   // read the input on analog pin 1:

   int sensorValue = analogRead(A1);
   // CR
   char 
   chrValueCR = 13;
   // Convert the analog reading (which goes from 0 - 1023 to
  
   //   a voltage (0 - 5V):
   
  //float voltage = sensorValue * (5.0 / 1023.0);

   // for Seismometer SEP model range is -32,768 to + 32,768
  
   int voltage = (sensorValue-511) * 63;  //63 is to keep from rolling the integer


   Serial.print(voltage);

   Serial.print(chrValueCR); 
   }
  


// the loop routine runs over and over again forever:

 void loop() {
    
 // everything happens in the interrupt

   
}