Understanding timer

[fan174]

If you have no real input on RC0 then you may need to pull the signal low when it should be low... Some need to be pulled high use a 10k resistor to either pull high or low.

I have a real signal. I think need to change program logic

 

[fan174]

If you have no real input on RC0 then you may need to pull the signal low when it should be low... Some need to be pulled high use a 10k resistor to either pull high or low.

When I used below code LED flash only one time

// PIC16F877A Configuration Bit Settings
// CONFIG
//MPLAB XC8
#pragma config FOSC = HS        // Oscillator Selection bits (HS oscillator)
#pragma config WDTE = OFF        // Watchdog Timer Enable bit (WDT enabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = ON       // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = OFF        // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3 is digital I/O, HV on MCLR must be used for programming)
#pragma config CPD = OFF        // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF        // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)
#define _XTAL_FREQ 20000000 //Specify the XTAL crystal FREQ
#include<xc.h>
void main(void)
{
    TRISC = 0b00000001;    //PORTC R0  pins are used as Input.
    TRISD = 0b00000000;    //PORTD R4  pins are used as output.
    //Loading starting value of counter 65536- 10 = 65426 = FFF6 hexa decimal
    TMR1H = 0xFF ;    // High byte FF
    TMR1L = 0xF6;    // Low Byte F6

    //Set T1CON Register
    TMR1ON  = 0; // Stops Timer1
    TMR1CS =  1; // Internal clock (FOSC/4)
    T1SYNC =  0; // Synchronize external clock input
    T1OSCEN = 1; // Oscillator is shut-off
    T1CKPS0 = 0;  //  1:8 prescale value
    T1CKPS1 = 0;
    
    TMR1IE=1; //Enable timer interrupt bit in PIE1 register
    GIE=1; //Enable Global Interrupt
    PEIE=1; //Enable the Peripheral Interrupt
    TMR1ON = 1; //Start Timer1
    
    while(1);
}

void interrupt timer_isr()
{
  if(TMR1IF ==1)
  {
    RD4 = 1;  // LED ON
    __delay_ms(500); //
    RD4 = 0;  // LED OFF
    
    TMR1IF=0; // Clear timer interrupt flag
    TMR1ON = 0; //Stop Timer1
    
    TMR1H = 0xFF ;    // High byte FF
    TMR1L = 0xF6;    // Low Byte F6
  }
}

 

[Ian Rogers]

When I used below code LED flash only one time

And?... How many flashes do you want?

 

[fan174]

And?... How many flashes do you want?

flash led when the sensor is a high repeat process

When I use below program led doesn't flash when sensor is high

// PIC16F877A Configuration Bit Settings

// CONFIG
#pragma config FOSC = HS        // Oscillator Selection bits (HS oscillator)
#pragma config WDTE = OFF        // Watchdog Timer Enable bit (WDT disable)
#pragma config PWRTE = OFF      // Power-up Timer Enable bit (PWRT disabled)
#pragma config BOREN = ON       // Brown-out Reset Enable bit (BOR enabled)
#pragma config LVP = OFF        // Low-Voltage (Single-Supply) In-Circuit Serial Programming Enable bit (RB3 is digital I/O, HV on MCLR must be used for programming)
#pragma config CPD = OFF        // Data EEPROM Memory Code Protection bit (Data EEPROM code protection off)
#pragma config WRT = OFF        // Flash Program Memory Write Enable bits (Write protection off; all program memory may be written to by EECON control)
#pragma config CP = OFF         // Flash Program Memory Code Protection bit (Code protection off)

#define _XTAL_FREQ 20000000 //Specify the XTAL crystal FREQ

#include<xc.h>

void main(void)
{
    TRISB = 0b00000001;    //PORTB R0  pins are used as Input.
    TRISC = 0b00000001;    //PORTC R0  pins are used as Input.
    TRISD = 0b00000000;    //PORTD R4  pins are used as output.
	
    //Loading starting value of counter 65536- 10 = 65426 = FFF6 hexa decimal
    TMR1H = 0xFF ;    // High byte FF
    TMR1L = 0xF6;    // Low Byte F6
   
   //Set T1CON Register
    TMR1ON  = 0; // Stops Timer1
    TMR1CS =  1; // Internal clock (FOSC/4)
    T1SYNC =  0; // Synchronize external clock input
    T1OSCEN = 1; // Oscillator is shut-off
    T1CKPS0 = 0;  //  1:8 prescale value
    T1CKPS1 = 0;
   
    TMR1IE=1; //Enable timer interrupt bit in PIE1 register
    GIE=1; //Enable Global Interrupt
    PEIE=1; //Enable the Peripheral Interrupt
    TMR1ON = 1; //Start Timer1
    while(1)
	
	{
	   if (RB0 == 0)
	   {
	      TMR1ON = 0; //Start Timer1
	   }
    }
}


void interrupt timer_isr()
{
  if(TMR1IF ==1)
  {
    RD4 = 1;  // LED ON
    __delay_ms(500); //
    RD4 = 0;  // LED OFF
    
    TMR1IF=0; // Clear timer interrupt flag
    TMR1ON = 0; //Stop Timer1
    
    TMR1H = 0xFF ;    // High byte FF
    TMR1L = 0xF6;    // Low Byte F6
  }
}

 

[fan174]

Hello Ian

Can you check the code on your board

 

[Ian Rogers]

What am I checking??? I still don't get the gist of the program.. If you explain what you would like it to do, I'll make it so...

At the moment I see 10 counts and the led flashes once to signify 10 counts... What else should it do?

 

[Dr_Doggy]

...

 

[fan174]

What am I checking??? I still don't get the gist of the program.. If you explain what you would like it to do, I'll make it so...

At the moment I see 10 counts and the led flashes once to signify 10 counts... What else should it do?

TRISC = 0b00000001; // count event RC0
TRISB = 0b00000001; //sensor
TRISD = 0b00000000; // LED

When object is detected by sensor , load TMR1 with starting value 25535 ( 63BF) so when TMR1 overflow it will generate interrupt so interrupt interrupt service routine will trigger the LED.

 

[Ian Rogers]

When object is detected by sensor , load TMR1 with starting value 25535 ( 63BF) so when TMR1 overflow it will generate interrupt so interrupt interrupt service routine will trigger the LED.

So where does the "count to10" come into it..

If you have a sensor on RB0 ( int pin ), Then what is driving the count on RC0 ?