伺服控制TMR2

大家好。我试图用PIC16F628A@20MHz的TMR2控制伺服电机。我把定时器设置为每隔1ms溢出（预分频器=4；TMR2寄存器=130），然后在中断例程中，伺服管脚被保持在高或低，因为代码显示：我的伺服正在移动大约2度。有些事情是非常错误的，一旦它从0点移动到180点，我会错过什么？



      以下为原文

    Hello guys. I was trying to control a servo motor using TMR2 of a PIC16F628A @20MHz.
I set the timer to overflow every 1ms (prescaler = 4; TMR2 register = 130), and then in the interrupt routine the servo pin is held high or low as the code shows:


// CONFIG
#pragma config FOSC = HS // Oscillator Selection bits (HS oscillator: High-speed crystal/resonator on RA6/OSC2/CLKOUT and RA7/OSC1/CLKIN)
#pragma config WDTE = OFF // Watchdog Timer Enable bit (WDT disabled)
#pragma config PWRTE = OFF // Power-up Timer Enable bit (PWRT disabled)
#pragma config MCLRE = ON // RA5/MCLR/VPP Pin Function Select bit (RA5/MCLR/VPP pin function is MCLR)
#pragma config BOREN = ON // Brown-out Detect Enable bit (BOD enabled)
#pragma config LVP = OFF // Low-Voltage Programming Enable bit (RB4/PGM pin has digital I/O function, HV on MCLR must be used for programming)
#pragma config CPD = OFF // Data EE Memory Code Protection bit (Data memory code protection off)
#pragma config CP = OFF // Flash Program Memory Code Protection bit (Code protection off)
#define _XTAL_FREQ 20000000
#include

unsigned char count, pos;

void interrupt ISR()
{
    if(TMR2IF)
    {
        if(pos >= count)
            PORTB = 0x04;
        else
            PORTB = 0;
        if (count == 200)
            count = 0;
        else
            count++;
    }
    TMR2 = 130;
    TMR2IF = 0;
}

void main(void)
{
    TRISB = 0;
    PORTB = 0;
    T2CON = 0x20;
    CCP1CON = 0;
    INTCON = 0xC0;
    PIE1 = 0x02;
    PIR1 = 0;
    count = 0;
    TMR2 = 130;
    TMR2ON = 1;
    while(1)
    {
        for(pos = 10; pos < 20; pos++)
            __delay_ms(500);
        for(pos = 20; pos > 10; pos--)
            __delay_ms(500);
    }
}


My servo is moving just around 2 degrees. Something is very wrong, once it should move from 0 to 180º and back.
What am I missing?

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