/* 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-bridges 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 terminal T3 and the jumper J4 should be at EXT.
 *
 * This program uses PORTB 3, 2 for direction control and PORTF 3 for
 * PWM control.  The outputs are terminals M3 and M4.
 * The PWM is generated by PWM1_3B.
 *
 * 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) {
    int pw = 0;

    SYSCTL->RCGCPWM |= 0x02;        // enable clock to PWM1
    SYSCTL->RCGCGPIO |= 0x20;       // enable clock to GPIOF
    SYSCTL->RCGCGPIO |= 0x02;       // enable clock to GPIOB
    
    delayMs(1);                     // PWM1 seems to take a while to start

    SYSCTL->RCC &= ~0x00100000;     // use system clock for PWM
    PWM1->INVERT |= 0x80;           // positive pulse
    PWM1->_3_CTL = 0;               // disable PWM1_3 during configuration
    PWM1->_3_GENB = 0x0000080C;     // output high when load and low when match
    PWM1->_3_LOAD = 3999;           // 4 kHz
    PWM1->_3_CTL = 1;               // enable PWM1_3
    PWM1->ENABLE |= 0x80;           // enable PWM1

    GPIOF->DIR |= 0x08;             // set PORTF 3 pins as output (LED) pin
    GPIOF->DEN |= 0x08;             // set PORTF 3 pins as digital pins
    GPIOF->AFSEL |= 0x08;           // enable alternate function
    GPIOF->PCTL &= ~0x0000F000;     // clear PORTF 3 alternate function
    GPIOF->PCTL |= 0x00005000;      // set PORTF 3 alternate funtion to PWM

    GPIOB->DEN |= 0x0C;             // PORTB 3 as digital pins
    GPIOB->DIR |= 0x0C;             // set PORTB 3 as output
    GPIOB->DATA |= 0x08;            // enable PORTB 3

    while(1) {
        // set direction
        GPIOB->DATA &= ~0x04;
        GPIOB->DATA |= 0x08;
        // ramp up speed
        for (pw = 100; pw < 3999; pw += 20) {
            PWM1->_3_CMPB = pw;
            delayMs(50);
        }
        // ramp down speed
        for (pw = 3900; pw >100; pw -= 20) {
            PWM1->_3_CMPB = pw;
            delayMs(50);
        }
        
        // reverse direction
        GPIOB->DATA &= ~0x08;
        GPIOB->DATA |= 0x04;
        // ramp up speed
        for (pw = 100; pw < 3999; pw += 20) {
            PWM1->_3_CMPB = pw;
            delayMs(50);
        }
        // ramp down speed
        for (pw = 3900; pw >100; pw -= 20) {
            PWM1->_3_CMPB = pw;
            delayMs(50);
        }
    }
}

/* 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 */
}