/* www.MicroDigitalEd.com
 * p6_4.c: Toggle the blue LED using the SysTick interrupt 
 * This program sets up the SysTick to interrupt at 1 Hz.
 * The system clock is running at 3 MHz, so
 * 3,000,000-1 for RELOAD register.
 * In the interrupt handler, the blue LED is toggled.
 *
 * Tested with Keil 5.20 and MSP432 Device Family Pack V2.2.0.
 */

#include "msp.h"

int main(void) {
    __disable_irq();

    /* initialize P2.2 for tri-color LEDs */
    P2->SEL1 &= ~4;           /* configure P2.2 as simple I/O */
    P2->SEL0 &= ~4;
    P2->DIR |= 4;             /* P2.2 set as output */

    /* Configure SysTick */
    SysTick->LOAD = 3000000-1;   /* reload with number of clocks per second */
    SysTick->CTRL = 7;           /* enable SysTick interrupt, use system clock */
    NVIC_SetPriority (SysTick_IRQn, 2); /* set priority to 2 */

    __enable_irq();              /* global enable interrupt */
    
    while (1) {
    }
}

void SysTick_Handler(void){
    P2->OUT ^= 4;    /* toggle the blue LED */
}