/* www.MicroDigitalEd.com
 * p5_3.c Toggling green LED using SysTick delay

 * This program uses SysTick to generate one second delay to
 * toggle the green LED.
 * master clock is running at 3 MHz. SysTick is configure
 * to count down from 3000-1 to 0 to give a 1 ms delay.
 * For every 1000 delays (1 ms * 1000 = 1 sec), toggle the
 * green LED once. The green LED is connected to P2.1.
 *
 * Tested with Keil 5.20 and MSP432 Device Family Pack V2.2.0
 * on XMS432P401R Rev C.
 */

#include "msp.h"

void delayMs(int n);

int main(void) {
    /* initialize P2.1 for green LED */
    P2->SEL1 &= ~2;         /* configure P2.1 as simple I/O */
    P2->SEL0 &= ~2;
    P2->DIR |= 2;           /* P2.1 set as output */

    while (1) {
        delayMs(1000);      /* delay 1000 ms */
        P2->OUT ^= 2;       /* toggle green LED */
    }
}

void delayMs(int n) {
    int i;
    SysTick->LOAD = 3000 - 1;   /* reload with number of clocks per millisecond */
    SysTick->VAL = 0;       /* clear current value register */
    SysTick->CTRL = 0x5;    /* Enable the timer */

    for(i = 0; i < n; i++) {
        while((SysTick->CTRL & 0x10000) == 0) /* wait until the COUNTFLAG is set */
            { }
    }
    SysTick->CTRL = 0;      /* Stop the timer (Enable = 0) */
}