/* p2_4.c Read SW0 on SAMD21 Xplained Pro 
 * and use the value to set the LED0.
 * SW0 is connected to PA15.
 * PA15 is configured to be input with pull-up.
 *
 * Tested with Atmel Studio 7 v7.0.1006 and Keil MDK-ARM v5.20
 */

#include "samd21.h"

int main (void) {
    unsigned char* ARRAY_PORT_PINCFG0 = (unsigned char*)&REG_PORT_PINCFG0;
    
    REG_PORT_DIRSET1 = 0x40000000;      /* make PB30 output for LED0 */
    REG_PORT_DIRCLR0 = 0x00008000;      /* make PA15 input for SW0 */
    ARRAY_PORT_PINCFG0[15] |= 6;        /* enable PA15 input buffer with pull */
    REG_PORT_OUTSET0 = 0x00008000;      /* make PA15 pull-up */
   
    /* LED shows state of SW0 */
    while(1) {
        if (REG_PORT_IN0 & 0x00008000)      /* check switch status */
            REG_PORT_OUTSET1 = 0x40000000;  /* turn off LED0 */
        else
            REG_PORT_OUTCLR1 = 0x40000000;  /* turn on LED0 */
    }
}