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echentj
Joined: 08 Dec 2011
Posts: 2
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| PIC16F877A ext Interrupt problem |
 Posted: Wed Dec 28, 2011 6:27 am |
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hi all,
My problem is my main program would not jump to external Interrupt when i press the button switch. I have connected a 5K pull up resistor to RB0 and a button switch which one end to ground and the other to RB0. I m using PCWH ver 3.219. Please help to rectify the problem. Thank you. | Code: |
#include <stdio.h>
#use delay(clock=20000000)
#fuses HS,NOWDT // and set the fuses
#int_EXT //denote the following function as the ISR for a falling edge on INT0
void ext_isr(void)
{
output_bit(pin_A5,0);
}
void main()
{
output_bit(pin_a5,1);
port_b_pullups(TRUE); //activate puulups on port B for ext interrupt
ext_int_edge(0,H_TO_L); //set external interrupt to falling edge
enable_interrupts(INT_EXT); // enable each interrupt
enable_interrupts(global); // allow the PIC to be interrupted
while(1) // just sit here.. and let the ISRs do the work
;
}
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Ttelmah
Joined: 11 Mar 2010
Posts: 19520
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| Posted: Wed Dec 28, 2011 9:03 am |
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I have just tidied the code a little, and run it, with your compiler version, and it works fine:
| Code: |
#include <16F877A.h>
#device adc=16
#FUSES NOWDT, HS, PUT, NOBROWNOUT, NOLVP
#use delay(clock=20000000)
#int_EXT //denote the following function as the ISR for a falling edge on INT0
void ext_isr(void) {
output_low(pin_A5);
}
void main(void) {
setup_comparator(NC_NC_NC_NC);
setup_spi(FALSE);
output_high(pin_a5);
port_b_pullups(TRUE); //activate pullups on port B for ext interrupt
ext_int_edge(H_TO_L); //set external interrupt to falling edge
clear_interrupt(INT_EXT); //it may have become set during initialisation
enable_interrupts(INT_EXT); // enable each interrupt
enable_interrupts(global); // allow the PIC to be interrupted
while(TRUE) // just sit here.. and let the ISRs do the work
delay_cycles(1);
}
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Only major tweaks were to clear the interrupt after setting it up, and ensure that the other things on pin A5, were turned off.
Like this, it runs.
Best Wishes |
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echentj
Joined: 08 Dec 2011
Posts: 2
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| 16F877A Interrupt problem |
| Posted: Wed Dec 28, 2011 10:20 pm |
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Hi Ttelmah,
Thank you for your effort, The code that you game me, it worked perfectly. But when i power down my circuit and power it up again, the LED will blink once only and then it goes off. Mean time i've added some statements to your code, but i still cant get it work. Below is the code that i had changed.
Kindly please comment. Thank you.
| Code: | #include <16F877A.h>
#device adc=16
#FUSES NOWDT, HS, PUT, NOBROWNOUT, NOLVP
#use delay(clock=20000000)
byte junk;
#int_EXT //denote the following function as the ISR for a falling edge on INT0
void ext_isr(void) {
output_low(pin_A5);
clear_interrupt(INT_EXT);
junk=input_b();
}
void main(void) {
setup_comparator(NC_NC_NC_NC);
setup_spi(FALSE);
output_high(pin_a5);
port_b_pullups(TRUE); //activate pullups on port B for ext interrupt
ext_int_edge(H_TO_L); //set external interrupt to falling edge
clear_interrupt(INT_EXT); //it may have become set during initialisation
enable_interrupts(INT_EXT); // enable each interrupt
junk=input_b();
enable_interrupts(global); // allow the PIC to be interrupted
junk=input_b();
while(TRUE) // just sit here.. and let the ISRs do the work
delay_cycles(1);
} |
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