Untitled

#include <xc.h>
#include <pic18f4520.h>
#define _XTAL_FREQ 125000 // Define clock frequency (125 kHz as per OSCCON)

#pragma config OSC = INTIO67 // Oscillator Selection bits
#pragma config WDT = OFF     // Watchdog Timer Enable bit
#pragma config PWRT = OFF    // Power-up Enable bit
#pragma config BOREN = ON    // Brown-out Reset Enable bit
#pragma config PBADEN = OFF  // Watchdog Timer Enable bit
#pragma config LVP = OFF     // Low Voltage (single -supply) In-Circute Serial Pragramming Enable bit
#pragma config CPD = OFF     // Data EEPROM?Memory Code Protection bit (Data EEPROM code protection off)

void main(void)
{
    // Timer2 -> On, prescaler -> 4
    T2CONbits.TMR2ON = 0b1;
    T2CONbits.T2CKPS = 0b01;

    // Internal Oscillator Frequency, Fosc = 125 kHz, Tosc = 8 microseconds
    OSCCONbits.IRCF = 0b001;

    // PWM mode, P1A, P1C active-high; P1B, P1D active-high
    CCP1CONbits.CCP1M = 0b1100;

    // CCP1/RC2 -> Output
    TRISC = 0;
    LATC = 0;
    TRISB = 0X01;//RB0 = input

    // Set up PR2, CCP to decide PWM period and Duty Cycle
    /**
     * PWM period
     * = (PR2 + 1) * 4 * Tosc * (TMR2 prescaler)
     * = (0x9b + 1) * 4 * 8?s * 4
     * = 0.019968s ~= 20ms
     */
    PR2 = 0x9b;

    /**
     * Duty cycle
     * = (CCPR1L:CCP1CON<5:4>) * Tosc * (TMR2 prescaler)
     * = (0x0b*4 + 0b01) * 8?s * 4
     * = 0.00144s ~= 1450?s
     */
    // 500  -> -90  => CCPR1L = 0X04
    // 1450 ->   0  => CCPR1L = 0X0B
    // 2400 -> +90  => CCPR1L = 0X14
    CCPR1L = 0x04;
    CCP1CONbits.DC1B = 0b01;
    int direction = 0; // 0->counterclockwise //1->clockwise
    while (1)
    {
        if (PORTBbits.RB0 == 0)
        {
            if (CCPR1L == 0x04) //-90
            {
                CCPR1L = 0x0b;
                direction = 0;
            }
            else if (CCPR1L == 0x0b) // 0
            {
                if (direction == 0) // counterclakwise
                    CCPR1L = 0x14;
                else // clockwise
                    CCPR1L = 0x04;
            }
            else if (CCPR1L == 0x14) //+90
            {
                CCPR1L = 0x0b;
                direction = 1;
            }
//            for (int i = 0; i < 1000; i++);
            __delay_ms(640);
        }
    }
    return;
}