/*
 * This program drives a stepper motor using half-step.
 * The EduBase board has a quad half-H-bridge motor driver
 * (TB6612FNG), 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 PB7-4.
 * These pins are shared with the LEDs.
 * The PWM inputs are connected to PB0 and PB1.  PWM function 
 * is not used in this program.  It is turned on 100%.
 *
 * 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 terminal T3 and the jumper J4 should be at EXT.
 *
 * PWM1 - PB0 - TIM8_CH2 - AF3
 * LED0 - PB4
 * LED1 - PB5
 *
 * PWM2 - PB1 - TIM8_CH3 - AF3
 * LED2 - PB6
 * LED3 - PB7
 */

#include "stm32f4xx.h"

void delayMs(int n);

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

    RCC->AHB1ENR |=  2;             /* enable GPIOB clock */
    
    GPIOB->MODER &= ~0x0000FF0F;    /* clear pin mode */
    GPIOB->MODER |=  0x00005505;    /* set pins to output mode */
    GPIOB->BSRR  =   0x00000003;    /* turn on PWM pins to enable the H-bridge */

    while(1) {
        GPIOB->BSRR = 0x00F00000;   /* clear motor enable pins */
        GPIOB->BSRR = halfsteps[i++ & 7] << 4;  /* set the motor enable pins */
        delayMs(100);
    }
}


/* 16 MHz SYSCLK */
void delayMs(int n) {
    int i;
    for (; n > 0; n--)
        for (i = 0; i < 3195; i++) ;
}