/* This program drives a stepper motor using half-step.
 *
 * The Wytec EduPad board has a quad half-H-bridge motor driver,
 * which is capable of driving two DC motors or a stepper motor 
 * with up to 15V and 1.2A continous current.
 * 
 * The enable pins of the half-bridge are connected to P2.5, P2.4,
 * P3.3, and P3.2. These pins are shared with the LEDs on the EduBase board.
 * The PWM inputs are connected to P2.7 and P2.6.
 *
 * The four output pins of the motor driver device are connected to
 * the blue terminals marked M1, M2, M3, and M4.  Use of external
 * power supply for motor is recommended.  External power should be
 * connected to the terminals T3 and the jumper J4 should be at EXT.
 *
 * Built and tested with MSP432P401R Rev. C, Keil MDK-ARM v5.24a and MSP432P4xx_DFP v3.1.0
 */

#include "msp.h"

void delayMs(int n);
void display(int data);

int main(void) {
    const char halfsteps[ ] = {0x9, 0x1, 0x5, 0x4, 0x6, 0x2, 0xa, 0x8};
    int i = 0;

    // Use PORTF3, 2 as PWM for motor control
    P2->DIR |= 0xC0;    /* P2.7, P2.6 set as PWM for motor control */
    P2->OUT |= 0xC0;    /* turn on P2.7 and P2.6 */ 
    
    P2->DIR |= 0x30;    /* P2.5, P2.4 set as output for half-bridge control */
    P3->DIR |= 0x0C;    /* P3.3, P3.2 set as output for half-bridge control */

    while(1) {
        display(halfsteps[i++ & 7]);   /* set the motor enable pins */
        delayMs(100);
    }
}

/* system clock at 3 MHz, MSP432P401R Rev. C, Start-up v2.2.1 */
void delayMs(int n) {
    int i, j;
    
    for (j = 0; j < n; j++)
        for (i = 750; i > 0; i--);      /* Delay */
}

void display(int data) {		
    if (data & 8)              /* bit 3 -> LED3 */
        P2->OUT |= 0x10;
    else
        P2->OUT &= ~0x10;
    
    if (data & 4)              /* bit 2 -> LED2 */
        P2->OUT |= 0x20;
    else
        P2->OUT &= ~0x20;
    
    if (data & 2)              /* bit 1 -> LED1 */
        P3->OUT |= 8;
    else
        P3->OUT &= ~8;
    
    if (data & 1)              /* bit 0 -> LED0 */
        P3->OUT |= 4;
    else
        P3->OUT &= ~4;        
}