/* p2_5.c
 *
 * Display number 35 on a 2-digit 7-segment common cathode LED.
 * The segments are driven by Port B.
 * The digit selects are driven by PA4 and PA5.
 *
 * Tested with Atmel Studio 7 v7.0.1006 and Keil MDK-ARM v5.20
 */

#include "samd21.h"

void delayMs(int n);

int main(void) {
    const unsigned char digitPattern[] = 
        {0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D, 0x7D, 0x07, 0x7F, 0x6F};

    REG_PORT_DIRSET1 = 0x0000007F;      /* make PB6-PB0 output */
    REG_PORT_DIRSET0 = 0x00000030;      /* make PA5-PA4 output */

    for(;;)
    {
        REG_PORT_OUT1 = digitPattern[3];    /* display tens digit */
        REG_PORT_OUTSET0 = 0x20;            /* deselect ones digit */
        REG_PORT_OUTCLR0 = 0x10;            /* select tens digit */
        delayMs(8);
        REG_PORT_OUT1= digitPattern[5];     /* display ones digit */
        REG_PORT_OUTSET0 = 0x10;            /* deselect ones digit */
        REG_PORT_OUTCLR0 = 0x20;            /* select tens digit */
        delayMs(8);  
    }
}

/* millisecond delay based on 8 MHz system clock */
void delayMs(int n) {
int i;
for (; n > 0; n--)
    for (i = 0; i < 199; i++)
        __asm("nop");
}