/* p6_2.c Interrupts from two I/O pins
 *
 * PA18 is configured to generate EIC interrupt through EXTINT2,
 * PA19 is configured to generate EIC interrupt through EXTINT3.
 * The interrupt handler blinks twice for EXTINT2 and three times
 * for EXTINT3.
 *
 * Tested with Atmel Studio 7 v7.0.1006 and Keil MDK-ARM v5.21a 
 */

#include "samd21.h"

unsigned char* ARRAY_PORT_PINCFG0 = (unsigned char*)&REG_PORT_PINCFG0;
unsigned char* ARRAY_PORT_PMUX0 = (unsigned char*)&REG_PORT_PMUX0;

void delayMs(int n);

int main (void) {
    __disable_irq();
    REG_PORT_DIRSET1 = 1 << 30;     /* make PB30 output for LED */
    
    ARRAY_PORT_PINCFG0[18] |= 7;    /* make PA18 EXTINT2 */
    ARRAY_PORT_PINCFG0[19] |= 7;    /* make PA19 EXTINT3 */
    ARRAY_PORT_PMUX0[9] = 0;        /* PA18 = EXTINT2, PA19 = EXTINT3 */
    REG_PORT_DIRCLR0 = 0xC0000;     /* PA18, PA19 input */
    REG_PORT_OUTSET0 = 0xC0000;     /* pull up PA18, PA19 */

    REG_GCLK_CLKCTRL = 0x4005;      /* GCLK0 -> EIC */
    REG_EIC_CONFIG0 |= 0x0000AA00;  /* EXTINT2/3 filtered falling-edge */
    REG_EIC_INTENSET = 0x000C;      /* enable EXTINT2/3 */
    REG_EIC_CTRL = 2;               /* enable EIC */
    NVIC_EnableIRQ(EIC_IRQn);
    __enable_irq();

    while(1) {
    }
}

/* in the interrupt handler, the yellow LED0 blinks twice */
void EIC_Handler(void) {
    if (REG_EIC_INTFLAG & 0x0004) {
        /* if interrupt is from EXTINT2, blink twice */
        REG_PORT_OUTCLR1 = 0x40000000; /* turn on LED */
        delayMs(250);
        REG_PORT_OUTSET1 = 0x40000000; /* turn off LED */
        delayMs(250);
        REG_PORT_OUTCLR1 = 0x40000000; /* turn on LED */
        delayMs(250);        
        REG_PORT_OUTSET1 = 0x40000000; /* turn off LED */
        delayMs(250);
        REG_EIC_INTFLAG = 0x0004;   /* clear interrupt flag */
    } else if (REG_EIC_INTFLAG & 0x0008) {
        /* if interrupt is from EXTINT3, blink three times */
        REG_PORT_OUTCLR1 = 0x40000000; /* turn on LED */
        delayMs(250);
        REG_PORT_OUTSET1 = 0x40000000; /* turn off LED */
        delayMs(250);
        REG_PORT_OUTCLR1 = 0x40000000; /* turn on LED */
        delayMs(250);        
        REG_PORT_OUTSET1 = 0x40000000; /* turn off LED */
        delayMs(250);
        REG_PORT_OUTCLR1 = 0x40000000; /* turn on LED */
        delayMs(250);        
        REG_PORT_OUTSET1 = 0x40000000; /* turn off LED */
        delayMs(250);
        REG_EIC_INTFLAG = 0x0008;   /* clear interrupt flag */
    } else {
        /* spurious interrupt?, clear all interrupt flags */
        REG_EIC_INTFLAG = REG_EIC_INTFLAG; /* clear all EIC interrupt flags */
    }
}
/* millisecond delay based on 1 MHz system clock */
void delayMs(int n) {
    int i;
    for (; n > 0; n--)
        for (i = 0; i < 199; i++)
            __asm("nop");
}