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RB interrupts on PIC16F84A

 
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Py
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RB interrupts on PIC16F84A
PostPosted: Tue May 04, 2004 9:35 am     Reply with quote
Hello,

I'm trying to get a very simple program to work: I have a bicolor led with its serail resistor connected between A2 and A3. I want to swap its color each time an rb intrrupt occurs. I tested the color swapping without interrupts using delay_ms(), and it works fine.

Now, I've added interrupts code, and led is in an unstable state, eg it swaps colors without any reason at any time, and don't when I want it to.

Here is the code:

Code:

#include <16f84a.h>
#fuses HS,NOWDT,PUT,NOPROTECT
#use delay(clock=4000000)

SHORT INT flag = 0;

#int_rb
rb_isr()
{
  if (flag) {
    flag = 0;
  }
  else {
    flag = 1;
  }
}

void main()
{
  //PORT_B_PULLUPS(TRUE);

  enable_interrupts(GLOBAL);
  enable_interrupts(INT_RB);
 
  while (TRUE) {
    if (flag) {
      output_high(PIN_A2);   
      output_low(PIN_A3);   
    }
    else {
      output_high(PIN_A3);   
      output_low(PIN_A2);   
    }
  }
}


I tried with and without the "PORT_B_PULLUPS(TRUE);" line, and it didn't change much. My opinion is that I'm missing something about PORTB configuration for the use I want to make of it.

My testing circuitry is simple: apart the quartz, and the 2 27pF capacitors, I only have the bicolor led and it resistor between A2 and A3, and a jumper between B4 and the ground to simulate button actions.

Thanks in adavnce for any hint!
Pierre-Yves Paulus
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Tue May 04, 2004 11:22 am     Reply with quote
Quote:
My opinion is that I'm missing something about PORTB
configuration for the use I want to make of it.

You need to clear the "mismatch" condition by reading Port B.
This is mentioned in Section 3.2 (i/o ports) of the 16F84A data sheet,
which you should read.

Example:

#byte port_b = 6

#int_rb
void int_rb_isr(void)
{
char c;

// Clear the mismatch condition by reading Port B.
c = port_b;

// Put the rest of your isr code here.

}
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