/* www.MicroDigitalEd.com
 * p5_2.c Toggling red LEDs at 1 Hz using SysTick
 *
 * This program uses SysTick to generate 1000 ms delay to
 * toggle the red LED.
 * Master clock is running at 3 MHz. SysTick is configured
 * to count down from 3,000,000-1 to give a 1s delay.
 * The red LED is connected to P2.0.
 *
 * Tested with Keil 5.20 and MSP432 Device Family Pack V2.2.0
 * on XMS432P401R Rev C.
 */

#include "msp.h"

int main(void) {
    /* initialize P2.0 for red LED */
    P2->SEL1 &= ~1;             /* configure P2.0 as simple I/O */
    P2->SEL0 &= ~1;
    P2->DIR |= 1;               /* P2.0 set as output */

    /* Configure SysTick */
    SysTick->LOAD = 3000000-1;  /* reload reg. with 3,000,000-1 */
    SysTick->VAL = 0;           /* clear current value register */
    SysTick->CTRL = 5;          /* enable it, no interrupt, use master clock */

    while (1) {
        if (SysTick->CTRL & 0x10000)    /* if COUNTFLAG is set */
            P2->OUT ^= 1;               /* toggle red LED */
    }
}