Timer2 Counter for Exteernal Pin

Development Libraries
1

How do you handle the Timer2 Counter for an External Pin ?

  • I need to use T2 because I am already using T0 and T1.

I came up with this code, but I do not know the pin, and it just seems to toggle continuously:

void loop()
{
  startCnt();

  long  i ;
  for(i=0; i<100000; i++)
  {
    /// make sure that loop is executed / not optimized out : ///
    PORTD |= 0x20 ;
  }

  GetTimer();
  Serial.println( timer2CounterValue  );
  delay(100);
}

void startCnt() 
{  
  overflow2Count = 0;

  // reset Timer 2
  TCCR2A = 0;
  TCCR2B = 0;

//  TIMSK2 = 2;   // enable Timer2 Interrupt
  TIMSK2 = 1;   // interrupt on Timer 1 overflow

  // set counter-2 to zero
  TCNT2 = 0;

  // External clock source on T2 pin (D???).  Clock on rising edge.
  TCCR2B = 7;
}

ISR (TIMER2_OVF_vect) 
{
  ++ overflow2Count;       // count number of Counter1 overflows
}

void GetTimer()
{
  /// Get TIMER T2 Counter : ///
  word          timer2CounterValue = TCNT2;  // 
  unsigned long overflow2Copy      = (overflow2Count);  // 

  TCCR2A = 0;    // stop timer 2
  TCCR2B = 0;

  TIMSK2 = 0;    // disable Timer2 Interrupt
}
2

I don't think T2 is able to be clocked from an usable external pin. It can use a clock or crystal connected to the pins that are already dedicated to the crystal...

3

Thanks for the response !

Actually though, I found an alternate way

  • (with T0 p4 and T1 p5) - that can give me a Total of 4 pins to Pulse Counters :
  • INT0 from pin 2
  • INT1 from pin 3

Example of INT0 from pin2 :

#include <avr/interrupt.h> 

long  myInt0Cnt = 0 ;

void setup(void) 
{ 
  pinMode(2, INPUT); 
  digitalWrite(2, HIGH);    // Enable pullup resistor 

  sei();                    // Enable global interrupts 
  // Global Enable INT0 interrupt
//  GICR |= ( 1 << INT0);
////  GICR |= ( 1 << INT1);
  EIMSK |= (1 << INT0);     // Enable external interrupt INT0 
  EICRA |= (1 << ISC01);    // Trigger INT0 on falling edge 
} 

void loop(void) 
{ 
  ;
} 

// Interrupt Service Routine attached to INT0 vector 
ISR(EXT_INT0_vect) 
{ 
  myInt0Cnt ++ ;

//  PORTB ^= (0x20);    // Toggle LED on pin 13 TEST  // - Fastest way
}

Example of INT1 from pin3 :

#include <avr/interrupt.h> 

long  myInt1Cnt = 0 ;

void setup(void) 
{ 
  pinMode(    3, INPUT); 
  digitalWrite(3, HIGH);    // Enable pullup resistor 

  // Global Enable INT1 interrupt
//  GICR |= ( 1 << INT0);
  GICR |= ( 1 << INT1);
//  EIMSK |= (1 << INT1);     // Enable external interrupt INT1 

  //falling edge interrupt 1
  MCUCR |= ( ( 0 << ISC10)  ||  ( 1 << ISC11) );
 }

void loop(void) 
{ 
  ;
} 

ISR(INT1_vect) 
{
  myInt1Cnt ++ ;

//  PORTB ^= (0x20);    // Toggle LED on pin 13 TEST  // - Fastest way
}