/* p10_2.c: Stepper motor control
 *
 * This program controls a unipolar stepper motor 
 * using P4.3, P4.2, P4.1, P4.0.
 *
 * Tested with Keil 5.20 and MSP432 Device Family Pack V2.2.0.
 */

#include "msp.h"

void delayMs(int n);

int delay = 10;
int direction = 0;

int main(void) {
    const char steps[ ] = {0x9, 0x3, 0x6, 0xC};
    int i = 0;

    P4->SEL1 &= ~0xF;             /* configure P4.0 as simple I/O */
    P4->SEL0 &= ~0xF;
    P4->DIR |= 0xF;               /* P4.0 set as output pin */

    while (1) {
        if (direction)
            P4->OUT = (steps[i++ & 3]);
        else
            P4->OUT = (steps[i-- & 3]);
        delayMs(delay);
    }
}

/* delay milliseconds when system clock is at 3 MHz */
void delayMs(int n) {
    int i, j;
    
    for (j = 0; j < n; j++)
        for (i = 250; i > 0; i--);      /* delay 1 ms */
}