/* www.MicroDigitalEd.com
 * p5_1.c Toggling LEDs using SysTick counter
 *
 * This program lets the SysTick counter run freely and dumps
 * the counter values to the tri-color LEDs continuously.
 * The counter value is shifted 21 places to the right so that
 * the changes of LEDs will be slow enough to be visible.
 * SysTick counter has 24 bits.
 * The blue LED is connected to P2.2.
 * The green LED is connected to P2.1.
 * 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) {
    int c;

    /* initialize P2.2-P2.0 for tri-color LEDs */
    P2->SEL1 &= ~7;             /* configure P2.2-P2.0 as simple I/O */
    P2->SEL0 &= ~7;
    P2->DIR |= 7;               /* P2.2-P2.0 set as output */

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

    while (1) {
        c = SysTick->VAL;       /* read current value of down counter */
        P2->OUT = c >> 21;      /* line up counter MSB with LED */
    }
}