Flash LED on and off every other second using TMR0. (Beginner coding question)

[Craig]

Hello, 

I am learning how to use TMR0 on a pic16f690.  I am trying to flash an led on and off every other second.  I am using the microchip low pin count board, a pickit 2 to program and MPLAB X to code and build the program with the MPLAB X compiler.  My code is below.  When i run the code on the board, the led lights up after about 5 seconds and just stays on.  No flashing or anything else.  Could anyone please tell me what i am doing wrong.  

Thank you for your help ahead of time!

 

#include <xc.h>

 #include <stdint.h>

 

// #pragma config statements should precede project file includes.

#pragma config MCLRE = OFF, CP = OFF, CPD = OFF, BOREN = OFF, WDTE = OFF

#pragma config PWRTE = OFF, FOSC = INTRCIO

 

#define _XTAL_FREQ 8000000  //pic16F690 OSC Frequency

 

void main()

{

    //ANSEL = 0b00000000;  //turn off analog, all ports are now digital output

    TRISC = ~(1<<1);  //Make RC1 an output

    PORTC = 0x00;  //Turn off all of the leds on PORTC

 

    OPTION_REGbits.T0CS = 0;  //select timer mode, not counter mode

    OPTION_REGbits.PSA = 0;  //assign prescalar to timer0

 

    //we will need to use a loop that goes around 250X to get 8ms.  (250x around at 32us will give us 8ms.)(.008/32us = 250)

    //then if we loop again 125X, we can get to 1 second (.008ms X 125 = 1 second, if we wanted a 1X every other second led flash)

    OPTION_REGbits.PS0 = 0b101;  //prescale = 64  (64/2,000,000 instruction cycle frequency = 32us, so the timer will tick every 32us)

 

    uint8_t a;

    

    for (;  //loop forever

    {

       for (a=0; a<125; a++)

         {

            TMR0 = 0 ; //reset TIMER 0

 

            while (TMR0 < 250)

             {

                ;;

             }

         }

 

       PORTCbits.RC1 = ~PORTCbits.RC1;

    }

}

[Ashutosh Bhatt]

first you go through our PIC tutorials given on

EG labs / micro controller / PIC

 

surely you will get idea whts going wrong in your application

 

[Author]

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