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Strange Problem with Timer1 on 18F4550 using PICKIT3

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ahmed osama

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i have a Strange Problem with Timer1 on 18F4550 using PICKIT3 (internal CLock 8 Mhz after OscCon 100 became 1Mhz)

the following code working so fine as there is a led turned on at the starting ( PORTDbits.RD2 = 1;) and after 30 sec , the timer1 will turn it off , it worked so fine but in cond. that while(1) must have inside it delay(); anything else the if cond. inside the timer1 ISR doesn't work at all

i tried the following

Code: 
while(1) { }
while(1);
while(1) { temp (); } //temp is just empty func.
for (1;;);

nothing makes the code run so well except when i use

Code: 
while(1)
{
delay(); // !!!!!!
}

sorry i am some how new to PIC programming so kindly help me

i also clear all mem , config bits ,....
i also cleared the project and rebuild it

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#include<p18f4550.h>
#include<timers.h>
 
 
void high_ISR (void);
void timer1_isr(void);
 
#pragma interrupt high_ISR //is already high
 
void high_ISR (void)
{
_asm goto timer1_isr _endasm
}
 
void delay(void);
 
int x;
void timer1_isr(void)
{
x=x+1;
if (x == 3750)
{
PORTDbits.RD2 = 0;
x=0;
}
PIR1bits.TMR1IF = 0; //Reset Timer1 interrupt flag
WriteTimer1(0xFC17); // Give new start value to the timer1
INTCONbits.GIEH  =1;
}
 
void main(void)
{ 
 
x=0;
 
INTCONbits.GIEH  =1;
 
   
 
TRISDbits.TRISD2 = 0;            // set RB0
 
  PORTDbits.RD2 = 1;        //  ON RB0
 
RCONbits.IPEN = 1; //Enable priority levels on interrupts
RCONbits.SBOREN = 0; //Disable BOR
 
IPR1bits.TMR1IP = 1; //Timer1 interrupt priority high
PIE1bits.TMR1IE = 1; //Timer1 interrupt enable
 
 OpenTimer1( TIMER_INT_ON & // Interrupt enabled
T1_16BIT_RW & //set timer1 as one 16-bit registers
T1_SOURCE_INT & //choose internal clock source (TOSC)
T1_PS_1_2 & // Prescale Value: 1:2
T1_OSC1EN_OFF & //Disable Timer1 oscillator
T1_SYNC_EXT_OFF //Don’t sync external clock input
);
 
WriteTimer1(0xFC17); // set start value of timer,
 
 
 
while(1)
{
delay();  // must delay func. and thing else the if cond. in the timer1 isr doesn't work
}
 
 
}
 
 
void delay(void) {
 
    int f, k;
 
 
 
    for(f=0; f < 1000 ; f++)
 
        for(k=0; k< 2 ; k++ )
{
        }
 
    }
 
Last edited by a moderator:

hello


Yes your clock seems to be 1Mhz
so timer1 interrupt every 8 mS * 3450 => give 30 secondes .. normal

but when you wrote
while(1)
{};

did you check what is the ASM given by the complier ?
maybe you can get the equivalent as
goto $-1

so there is no gap to go out of the main programme and return inside
maybe it can work with some additional NOP like this..

ici:
nop
nop
goto ici



it is not a NORMAL SITUATION ..
the main job must be done by the main programme , not only by interrupts.
 

i have put nop inside while(1) and didn't worked , but there is another more strange when i changed the for loop inside the delay from 1000 to 10 it does not work !!!
 

hello

try this :
Raz the interrupt flag at the end of ISR
you don't need to arm GIE .

To do a tempo of 30 sec
maybe it's better to use the max capacity ot timer1
to reduce the number of interrups ;
for example :
with a value of 3035 (0x0BDB) and with prescaler=1/8 (instead of 1/2)
you get 2000mS instead of 8 ms
so count maxi= 30/2=15 to obtain 30 secondes

Code: 
void timer1_isr(void)
{
x=x+1;
if (x == 3750)
{
PORTDbits.RD2 = 0;
x=0;
}

WriteTimer1(0xFC17); // Give new start value to the timer1
PIR1bits.TMR1IF = 0; //Reset Timer1 interrupt flag
}
 

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