creating PWM using PIC

allbits said:

From you older posts, I understand, you have a continuous rotation servo. And that you need to rotate the shaft 180 degrees to the right and to the left, in a loop.
try this -
1) Write a subroutine to turn the motor to the left - say, goLeft();
2) Write another to turn to right - say goRight();
Find the time for the shaft to reach your 180 degrees. Write a subroutine for the time delay

call goLEft and goRight with the delay subroutine in between, and put the entire thing in a loop.

This is, assuming you know how to turn your motor to the left and to the right. If you have variations in the load at shaft, the time will change. If the positioning is critical, put a sensor at the 180 degree point. Then wait for the shaft to reach that point before you call either of the goLeft or goRight subroutines.

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hi allbits
i dont understand what you are saying
i just need the asm/C file

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Nigel Goodwin said:

No, servos only have a fairly limited movement - which the specs don't seem to mention?.

It certainly couldn't be 270 degrees in each direction, that would require 540 degrees total movement, and the pot can only move a possible maximum of 270 degrees.

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Pommie said:

Here you go, BoostC source code for a 16F886.

Code:

#include <system.h>

#pragma DATA _CONFIG, _DEBUG_ON & _MCLRE_ON
                    & _CP_OFF & _PWRTE_OFF
                    & _WDT_OFF & _INTOSCIO
                    & _LVP_OFF
#pragma CLOCK_FREQ 8000000

#define Servo portb.0
#define ServoTris trisb.0

void WaitInt();
unsigned int Position;
unsigned char PK2_reserved@0x70;
unsigned int ccp1 @CCPR1L;

void main(void){
    while(!osccon.HTS);
    osccon=0x71;                //8 meg
    ansel=0;
    anselh=0;
    adcon1=0x0f;
    ServoTris=0;                //make servo pin output
    Servo=0;                    //Servo output off
    ccp1con=0b00001011;         //Special event trigger
    t1con=0b10010001;           //Timer 1 on with Pre=2
    Position=1500;              //set servo to mid position
    pie1.CCP1IE=1;
    intcon.GIE=1;
    intcon.PEIE=1;
    while(1){
        while(Position<2000){
            WaitInt();
            Position+=10;
        }
        while(Position>1000){
            WaitInt();
            Position-=10;
        }

    }
}

void WaitInt(){
    while(Servo);       //wait for low
    while(!Servo);      //wait for high
}

void interrupt(void){
    if(Servo){
        Servo=0;
        ccp1=20000-Position;
    }else{
        Servo=1;
        ccp1=Position;
    }
    pir1.CCP1IF=0;
}

The above uses the internal oscillator and outputs the pulse on B0. It takes 2 seconds to go from one extreme to the other.

Mike.

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