/*
 * This program drives a standard servo motor.
 *
 * The PWM1 Generator 3B is used 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->RCGCPWM |= 0x02;        // enable clock to PWM1
    SYSCTL->RCGCGPIO |= 0x20;       // enable clock to GPIOF
    SYSCTL->RCGCGPIO |= 0x02;       // enable clock to GPIOB

    SYSCTL->RCC |= 0x00100000;      // enable clock divider for PWM
    SYSCTL->RCC &= ~0x000E0000;     // clear clock divide
    SYSCTL->RCC |=  0x00040000;     // set clock divide to 8 (16 MHz / 8 = 2 MHz)
    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 = 40000 - 1;      // 50 Hz
    PWM1->_3_CMPB = 2000 - 1;       // 1000 us
    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 |= 0x08;             // PORTB 3 as digital pins
    GPIOB->DIR |= 0x08;             // set PORTB 3 as output
    GPIOB->DATA |= 0x08;            // enable PORTB 3

    while(1)
    {
        for (pw = 2000 - 1; pw < 4000 - 1; pw += 50)
        {
            PWM1->_3_CMPB = 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;
}