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Twitie
Joined: 08 Nov 2004
Posts: 11
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| Need help in RB0 external interrupt |
 Posted: Wed Nov 10, 2004 3:26 am |
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| Code: |
#include <16f877a.h>
#fuses HS,NOLVP,NOWDT,PUT
#use delay(clock=20000000)
int1 found_it;
#int_ext
void ext_isr()
{
found_it = true;
}
void main()
{
found_it = false;
set_tris_b(0x01);
enable_interrupts(global); // set GIE in INTCON register
enable_interrupts(int_ext); // set INTE in INTCON register
ext_int_edge(H_TO_L); // initially RB0 is high (button is not pressed)
// clear INTEDG in OPTION_REG register
while(TRUE)
{
if (found_it)
{
found_it = false;
output_high(PIN_D1);
delay_ms(2000);
}
output_high(PIN_D1);
delay_ms(300);
output_low(PIN_D1);
delay_ms(300);
}
}
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I write this for RB0 interrupt but it don't work. I have studied the datasheet and follow the requirement. Is there any important point I miss out? Anyone can help me? THX! |
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Juan Pablo
Guest
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| Problem with RB0 interrupt |
| Posted: Wed Nov 10, 2004 5:34 am |
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Try putting the next lines of code in this order:
...
ext_int_edge(H_to_L);
enable_interrupts(INT_EXT);
enable_interrupts(GLOBAL);
...
Best Wishes. |
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ckielstra
Joined: 18 Mar 2004
Posts: 3680
Location: The Netherlands
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| Posted: Wed Nov 10, 2004 5:45 am |
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Have you checked the voltage levels on input pin_B0? Are they 5V with switch open and 0V with the switch closed?
Please note that by default the internal pull-up resistors on port-b are disabled, so you either need external pull-up resistors or use PORT_B_PULLUPS(TRUE) for enabling the internal pull-ups. |
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Twitie
Joined: 08 Nov 2004
Posts: 11
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| Posted: Thu Nov 11, 2004 7:58 pm |
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My port RB0 is initially high(5V). It turns to low when I press the button. I have set the port_b_pullups but still cannot work... 
| Code: |
........
found_it = false;
set_tris_b(0x01);
ext_int_edge(H_TO_L);
enable_interrupts(int_ext);
enable_interrupts(global);
port_b_pullups(TRUE);
.......
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Thu Nov 11, 2004 8:38 pm |
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| You don't have anything else attached to portb do you? Namely RB0? I tried an experiment with a PICDEM2 Plus board. RB0 has an LED on it along with RB3-RB1. I wanted to use one of the another LEDs but enabling the LEDs with the jumper caused a problem. Otherwise, the code worked fine and I got the int. |
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Twitie
Joined: 08 Nov 2004
Posts: 11
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| Posted: Thu Nov 11, 2004 8:56 pm |
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| Quote: |
You don't have anything else attached to portb do you? Namely RB0? I tried an experiment with a PICDEM2 Plus board. RB0 has an LED on it along with RB3-RB1. I wanted to use one of the another LEDs but enabling the LEDs with the jumper caused a problem. Otherwise, the code worked fine and I got the int.
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Do you mean that all the portb pins should be 'free'? I connect my RB0 to a button (initially open) and my RD1 to a LED. |
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Mark
Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA
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| Posted: Thu Nov 11, 2004 9:58 pm |
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| Quote: | | Do you mean that all the portb pins should be 'free'? |
No, just RB0 |
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Twitie
Joined: 08 Nov 2004
Posts: 11
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| Posted: Thu Nov 11, 2004 10:35 pm |
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I connect my RB0 to a normally-open push button. This connection is correct right?
................ __
RB0 --------o o-------- Gnd
............push buttton
and I internally pull port b to high using "port_b_pullups(TRUE);" and clear the INTEDG using "ext_int_edge(H_TO_L);".
Since you have tested my code and it is working.... I think I have to check my circuit. |
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