Timer0 Library

This library is written in C for the PIC16F877A and is designed to generate accurate delays using Timer0. It is compatible with MPLAB and relies on direct register access for maximum control and performance.

Library Routines

• bTimerInit
• bTimerRegCallback
• bTimerUnregCallback
• vTimerDelayMs

Library Routine	Prototype	Description	Return Value
bTimerInit	bool bTimerInit(void);	Initializes Timer0 and prepares it for use.	true if the timer was successfully initialized; false otherwise.
bTimerRegCallback	bool bTimerRegCallback(cbkFunc_t Function, uint32_t u32PeriodMs);	Registers a callback function to be triggered periodically by Timer0.	true if the function was successfully registered; false otherwise.
bTimerUnregCallback	bool bTimerUnregCallback(cbkFunc_t Function, uint32_t u32PeriodMs);	Unregisters a previously registered callback function.	true if the function was successfully unregistered; false otherwise.
vTimerDelayMs	void vTimerDelayMs(uint32_t u32Delay);	Generates a blocking delay in milliseconds using Timer0.	None

Library Example

// Specify the XTAL crystal at 20Mhz
#define _XTAL_FREQ  20000000 
#include "config.h"
#include <xc.h>
#include "hw_desc_timer.h"

#define LED_PIN     PORTBbits.RB0
#define LED_DIR     TRISBbits.TRISB0
#define DIR_INPUT   1
#define DIR_OUTPUT  0
#define CLEAR_PIN   0
#define SET_PIN     1


/* Led toggle function */
void vLedToggle(void)
{
    LED_PIN = ~LED_PIN;
}


/*  main function */
void main(void) {

    /* Configuration of pin 0 of PORTB as output */
    LED_DIR = DIR_OUTPUT;

    /* Initialization of PORTB */
    LED_PIN = CLEAR_PIN;

    /* Initialization of timer 0 */
    bTimerInit();

    /* Registration of callback function */
    /* Toggle led every 500ms */
    bTimerRegCallback(vLedToggle, 500);

    while(1)
    {
    }

    return;
}