/* 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 PORTB 3-0.
 * The PWM inputs are connected to PORTF 2 and PORTF 3.  These
 * pins are shared with the LEDs.  The PORTB pins are connected to
 * the LEDs on the EduBase board.  The PORTF pins are connected to
 * the LEDs on the Tiva LaunchPad.
 *
 * 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 Keil MDK-ARM v5.24a and TM4C_DFP v1.1.0
 */

#include "TM4C123.h"

void delayMs(int n);

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

    SYSCTL->RCGCGPIO |= 0x20;   // enable clock to GPIOF
    SYSCTL->RCGCGPIO |= 0x02;   // enable clock to GPIOB

    // Use PORTF3, 2 as PWM for motor control
    GPIOF->DIR = 0x0C;          // set PORTF3, 2 pins as output pin
    GPIOF->DEN = 0x0C;          // set PORTF3, 2 pins as digital pins
    GPIOF->DATA = 0x0C;         // assert PWM for now
    
    GPIOB->DEN |= 0x0F;         // PORTB 3-0 as digital pins
    GPIOB->DIR |= 0x0F;         // set PORTB 3-0 as output

    while(1) {
        GPIOB->DATA &= ~0x0F;       // clear motor enable pins
        GPIOB->DATA |= halfsteps[i++ & 7];  // set the motor enable pins
        delayMs(100);
    }
}

/* delay n milliseconds (50 MHz CPU clock) */
void delayMs(int n) {
    int i, j;
    for(i = 0 ; i< n; i++)
        for(j = 0; j < 6265; j++)
            {}  /* do nothing for 1 ms */
}