/*
 * 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 Timer1B.
 */

#include "TM4C123GH6PM.h"

void delayMs(int n);
void delayUs(int n);

int main(void)
{
    int pw = 0;

    SYSCTL->RCGCTIMER |= 0x02;      // enable clock to TIMER1
    SYSCTL->RCGCGPIO |= 0x20;       // enable clock to GPIOF
    SYSCTL->RCGCGPIO |= 0x02;       // enable clock to GPIOB

    TIMER1->CTL &= ~0x0100;         // disable TIMER1B during setup
    TIMER1->CFG = 4;                // configure as 32-bit timer mode
    TIMER1->TBMR = 0x0A;            // down-count, PWM-periodic mode
    TIMER1->TBILR = 3999;           // 16 MHz / 4000 = 4 kHz  
    TIMER1->CTL |= 0x4100;          // enable TIMER1B

    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 |= 0x00007000;      // set PORTF 3 alternate funtion to timer

    GPIOB->DEN |= 0x0C;             // PORTB 2, 3 as digital pins
    GPIOB->DIR |= 0x0C;             // set PORTB 2, 3 as output
    GPIOB->DATA |= 0x08;

    while(1)
    {
        // speed up
        for (pw = 100; pw < 3999; pw += 20)
        {
            TIMER1->TBMATCHR = pw;
            delayMs(50);
        }
        // slow down
        for (pw = 3900; pw >100; pw -= 20)
        {
            TIMER1->TBMATCHR = pw;
            delayMs(50);
        }
        // change dirction
        GPIOB->DATA &= ~0x08;
        GPIOB->DATA |= 0x04;
        
        // speed up
        for (pw = 100; pw < 3999; pw += 20)
        {
            TIMER1->TBMATCHR = pw;
            delayMs(50);
        }
        // slow down
        for (pw = 3900; pw >100; pw -= 20)
        {
            TIMER1->TBMATCHR = pw;
            delayMs(50);
        }
        // change dirction
        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;
}