SERVO MOTOR INTERFACE USING PWM:

C CODE:

MAIN PROGRAM:

#include <p89v51rd2.h>
#include "servo.h"

void PowerOn()
{
    unsigned char inner, outer;

    IE = 0x00;
    P1 = 0xFF; /* Motor STOP */

    for (outer = 0x00; outer < 0x10; outer++) { /* Delay for a while */
        for (inner = 0x00; inner < 0xFF; inner++);
    }

    Servos_init();

    IE = 0x80; /* Start interrupt */
}

void main()
{
    PowerOn();

    ServoR_forward();
    ServoL_back();

    while (1);
}

SERVO HEADER C SOURCE FILE:
/*
 * Filename : servos.h
 * Hardware : Controller  -> P89V51RD2
 *            XTAL        -> 11.0592 MHz
 *            Mode        -> 6 Clock/MC
 * I/O      : P1.4        -> Left  (PWM-CEX1)
 *            P1.5        -> Right (PWM-CEX2)

/* Control the Left servo */
void ServoL_back()
{
    CCAP1H = 243;
}

void ServoL_forward()
{
    CCAP1H = 230;
}

void ServoL_stop()
{
    CCAP1H = 0;
}


/* Control the Right servo */
void ServoR_back()
{
    CCAP2H = 230;
}

void ServoR_forward()
{
    CCAP2H = 243;
}

void ServoR_stop()
{
    CCAP2H = 0;
}


/* Initialize the PCA and PWM mode */
void Servos_init()
{
/* Initial Timer0 Generate Overflow PCA */

    TMOD = 0x02;   /* Timer0 Mode2 : 8bit auto reload */
    TH0  = 16;     /* 256-240, 8.125usec Auto-relead (20msec/PWM) */
    TL0  = TH0;
    TCON = 0x10;   /* setb TR0, TCON or 0001,0000*/

/*
    Initial PWM Period  = 20mS (11.0592MHz /6-Cycle Mode)
    Initial PCA Count From Timer0 Overflow
    1 Cycle of Timer0 = (1/11.0592MHz)x6 = 0.543uS
    Timer0 AutoReload = 240 Cycle = 78.125uS
    1 Cycle PCA = [(1/11.0592MHz)x6]x240 = 78.125uS
    Period 20mS of PCA = 20ms/78.125us = 256(CL Reload)
    CL(20mS) = 256 Cycle Auto Reload
    Load CCAPxH(1.0mS) = 256-13 = 243 (243,244,...,255 = 13 Cycle)
    Load CCAPxH(2.0mS) = 255-26 = 230 (230,231,...,255 = 26 Cycle)
*/
    CMOD=0x04;
    CCAPM1=0x42;
    CCAPM2=0x42;
    CCAP1H=0x00;
    CCAP2H=0x00;
    CCON=0x40;
}