/*
 * This program drives a standard servo motor.
 *
 * The Timer1B is used in PWM mode to generate a 50 Hz signal
 * with pulse width between 1 ms and 2 ms.
 * The quad half-H-bridge motor driver (TB6612FNG) of Wytec EduBase board
 * is configured so that the output of the PWM is also available at M4 terminal.
 *
 */

#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 = (320000 - 1) & 0xFFFF;  // 16 MHz / 320000 = 50 Hz
    TIMER1->TBPR = (320000 - 1) / 0x10000;
    TIMER1->TBMATCHR = 16000 - 1;
    
    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 |= 0x08;             // PORTB 3 as digital pins
    GPIOB->DIR |= 0x08;             // set PORTB 3 as output
    GPIOB->DATA |= 0x08;            // enable PORTB 3

    while(1)
    {
        for (pw = 16000 - 1; pw < 32000 - 1; pw += 400)
        {
            TIMER1->TBMATCHR = pw;
            delayMs(100);
        }
    }
}

// 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;
}