/* This program controls the rotational speed and direction of 
 * a DC motor.
 *
 * 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 continuous 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 EduPad 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 terminal T3 and the jumper J4 should be at EXT.
 *
 * This program uses P3.3 and P3.2 for direction control and P2.7 for
 * PWM control.  The outputs are terminals M1 and M2.
 * The PWM is generated by Timer A0.4.
 *
 * 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);

int main(void) {
    int pw;
    
	/* Configure P2.7 as Timer A0.4 output */
    P2->SEL0 |= 0x80;
    P2->SEL1 &= ~0x80;
    P2->DIR |= 0x80;

    P3->DIR |= 0x0C;    /* P3.3, P3.2 set as output for half-bridge control */

    /* configure TimerA0.4 as PWM */
    TIMER_A0->CCR[0] = 299;     /* PWM Period */
    TIMER_A0->CCR[4] = 299;     /* CCR4 PWM duty cycle */
    TIMER_A0->CCTL[4] = 0xE0;   /* CCR4 reset/set mode */
    TIMER_A0->CTL = 0x0214;     /* use SMCLK, count up, clear TA0R register */

    while(1) {
        // set direction
        P3->OUT &= ~0x04;
        P3->OUT |=  0x08;
        // ramp up the pulse width
        for (pw = 10; pw < 300; pw += 2) {
            TIMER_A0->CCR[4] = pw;
            delayMs(50);
        }
        
        // ramp down the pulse width
        for (pw = 299; pw > 10; pw -= 2) {
            TIMER_A0->CCR[4] = pw;
            delayMs(50);
        }
        
        // reverse direction
        P3->OUT &= ~0x08;
        P3->OUT |=  0x04;
        // ramp up the pulse width
        for (pw = 10; pw < 300; pw += 2) {
            TIMER_A0->CCR[4] = pw;
            delayMs(50);
        }
        
        // ramp down the pulse width
        for (pw = 299; pw > 10; pw -= 2) {
            TIMER_A0->CCR[4] = pw;
            delayMs(50);
        }
    }
}

/* 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 */
}