/*
 * This program controls the rotational speed and direction of 
 * a DC motor.
 *
 * The Wytec 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 PORTB 3-0.
 * The PWM inputs are connected to PORTF 1 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.
 */
#include "TM4C123GH6PM.h"

void delayMs(int n);
void delayUs(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

    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)
    {
        for (pw = 100; pw < 3999; pw += 20)
        {
            PWM1->_3_CMPB = pw;
            delayMs(50);
        }
        for (pw = 3900; pw >100; pw -= 20)
        {
            PWM1->_3_CMPB = pw;
            delayMs(50);
        }
        GPIOB->DATA &= ~0x08;
        GPIOB->DATA |= 0x04;
        for (pw = 100; pw < 3999; pw += 20)
        {
            PWM1->_3_CMPB = pw;
            delayMs(50);
        }
        for (pw = 3900; pw >100; pw -= 20)
        {
            PWM1->_3_CMPB = pw;
            delayMs(50);
        }
        GPIOB->DATA &= ~0x04;
        GPIOB->DATA |= 0x08;
    }
}

// delay n milliseconds (16 MHz CPU clock)
void delayMs(int n)
{
    int i, j;
    for(i = 0 ; i < n; i++)
        for(j = 0; j < 3180; j++)
            {}  // do nothing for 1 ms
}

// delay n microseconds (16 MHz CPU clock)
void delayUs(int n)
{
    int i, j;
    for(i = 0 ; i < n; i++)
        for(j = 0; j < 3; j++)
            {}  // do nothing for 1 us
}

// This function is called by the startup assembly
// code to perform system specific initialization tasks.
void SystemInit(void)
{
    // Grant coprocessor access
    // This is required since TM4C123G has
    // a floating point coprocessor
    SCB->CPACR |= 0x00f00000;
}