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cembeddedavratmelatmelstudio

Only two IO port interrupts for Xmega (INT0 and INT1)

In avr Xmega device, there are only two IO port interrupt vectors INT0 and INT1.

I have three switches that should generate three interrupts. I have written an interrupt code for the first switch using INT0. Now, I can write the second interrupt using INT1 which will exhaust my vectors. Below is my code for INT0 ISR:

ISR (PORTD_INT0_vect){
PORTD.INTFLAGS = 0x01; // clear INT0IF flag.

PORTD_OUT = PORTD_OUT | (1<<4); // led on.

}

Can I redefine this ISR to enable interrupt for second switch?

The registers that I set in main function are as follows:

PORTD.INT0MASK = 0x04; // PD2 is the source of interrupt for INT0.
PORTD.INTCTRL = 0x03; // Disable INT1, enable INT0 and place it a high-priority level.
PORTD.PIN2CTRL = 0x03; // configure PD2 pin to interrupt on the low level of signal.
PMIC.CTRL = 0x07;    // enable high,medium, and low level interrupts.
sei();         // enable interrupt globally.
Solution

  • The idea of the external interrupts is that you get to know that something happened, but not what happened. In your ISR you have to read out the state of the inputs the switches are connected to and determine based on the readout, what to do. To detect, if the state did alter, keep a copy of the ports input status and do an XOR with the newly read out value (do this for a whole port, not just for single pins).