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mofuzz
Joined: 14 Sep 2006
Posts: 1
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| Weird behavior with interrupt |
 Posted: Tue Jun 19, 2007 2:04 pm |
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Hello knowledgeable pic peeps.
I'm trying to do a simple routine using the rb_isr interrupt. The interrupt routine works ok. Basically my simple program toggles between 2 led patterns depending on whether the interrupt is true (i have a switch on pin b4 going to gnd with a 1k weak pullup).
My problem is that when I turn on the pic, it just sits there and doesn't do anything. It doesn't do the default routine or the interrupt routine, despite the fact that I tried to init the status variable in main().
As soon as I do the interrupt one time, it starts to work and works from then on! When i comment out the enable_interrupts it runs the default routine.
I'm sure I'm overlooking something obvious. Can someone help me out?
thanks!
| Code: |
#include <16F88>
#include <STDLIB.h>
#fuses INTRC,NOWDT,NOPROTECT,NOLVP, NOBROWNOUT, NOMCLR /* set the configuration bits*/
#use standard_io(A)
#use standard_io(B) /* use standard_io - this will normally always be included
in your files */
#use delay(clock=8000000) /* tell the compiler what speed xtal or clock you are running your pic at.
This is important so that it gets the delay_ms() calls below
correct */
# byte port_b = 6 //sets up port_b as a variable
int state=0; //the interrupt flag
static char dummy;
#int_rb
rb_isr() { //this interrupt function is called when any of port b pins B4-B7 change states
dummy = port_b; //read port_b
if(input(PIN_B4) == 0) { //testing B4 for interrupt switch
output_low(PIN_B0); //turn off status led to show interrupt has occurred
state=1;
}
}
void status_led() {
output_high(PIN_B0);//turns on led for normal state
}
void pattern_1(){ //do this pattern during the interrupt
output_high(PIN_A0);
delay_ms(50);
output_low(PIN_A0);
state=0;
}
void pattern_2(){ //do this pattern in normal state
output_high(PIN_A1);
delay_ms(100);
output_low(PIN_A1);
delay_ms(100);
output_high(PIN_A2);
delay_ms(100);
output_low(PIN_A2);
}
main() {
setup_oscillator(OSC_8MHZ|OSC_INTRC); //set up internal oscillator to run at 8mhz
enable_interrupts(INT_RB); /* enable RB interrupt (port B input interrupt) */
enable_interrupts(GLOBAL); /* start the interrupts running */
// dummy = port_b; //read port_b
state=0; //init the state
while (true) {
status_led(); //led on during normal state
if (state==1){
pattern_1();
}
else if (state==0){
pattern_2();
}
delay_ms(20);
} /*end of while loop*/
}
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue Jun 19, 2007 2:41 pm |
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I didn't look at your program in detail, but before you enable interrupts
in main(), you should:
1. Read Port B to clear the mis-match condition.
2. Call the clear_interrupt() function with INT_RB as the parameter.
By doing these things, you ensure that you don't start out with
a pre-existing interrupt condition.
Your code shows that you were trying to partially do this, by reading
port B. But it's commented out, and the location of the line is wrong.
It must be done before you enable interrupts in main(). |
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Guest
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| Posted: Tue Jun 19, 2007 5:48 pm |
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| Thanks! That fixed it. |
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