Hi,
Hardware environment: Im using an Arduino 2560. Blinking LED, on digital output port 4. Port 4 is also connected to digital input poort 2.
Problem: I have setup an Interrupt Service routine which is triggered on a falling edge of interrupt 0 (port 2). Within the Interrupt Service Routine (ISR) I just increment a counter. I assume when the LED is blinking 5 times, the counter in the ISR displays 5. However the counter displays 254. How is that possible ?
Software:
#include <avr/io.h>
#include <avr/interrupt.h>
#include <avr/pgmspace.h>
#include <stdint.h>
#include <string.h>
#include “bits.h” //Library to use bit functions
#define PORT_PG_DDRG DDRG
#define PORT_G PORTG
char buffer[50];
int interruptHandlerCalled;
void setup()
{
// PORTG maps to Arduino digital pin 5
PORT_PG_DDRG = PORT_PG_DDRG | B00100000; // set PORTG (digital 5) to output
// Install interrupt handler “LEDIsBlinking” on digital I/O pin 2.
attachInterrupt(0, LEDIsBlinking, FALLING); //pin 2
Serial.begin(115200);
}
void loop()
{
int nrOfTimesBlinking, // Defines how many times the LED will blink
delayBlinking; // Defines the delay between the blinking time of the LED
uint8_t pinLayout;
delayBlinking = 500; // Delay between the LED is on and off
// PORTG PG5 maps to Arduino 2560 digital pin 4.
pinLayout = B00100000;
interruptHandlerCalled = 0;
for (nrOfTimesBlinking = 0; nrOfTimesBlinking < 5; nrOfTimesBlinking++)
{
PORT_G = pinLayout;
delay(delayBlinking);
PORT_G = PORT_G & ~pinLayout;
delay(delayBlinking);
}
sprintf(buffer, “Number of interrupts is: %d”, interruptHandlerCalled);
Serial.println(buffer);
delay(1000);
}
void LEDIsBlinking()
{
interruptHandlerCalled++;
}