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weg22
Joined: 08 Jul 2005
Posts: 91
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| external interrupts (trouble with CCP1) |
 Posted: Thu Aug 11, 2005 12:34 pm |
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If I have pin B0 (my ccp pin) grounded, can someone please tell me why A2 is going high?
Thanks
| Code: |
#include <16F87.H>
#include <stdlib.h>
#include <math.h>
#define A2 PIN_A2
#define B0 PIN_B0
#define B1 PIN_B1
#define B2 PIN_B2
#fuses HS,NOWDT,NOPROTECT, PUT
#use delay(clock=4000000)
long rise, fall, pulseLength;
#int_ccp1
void isr()
{
pulseLength=0;
set_timer1(0);
while(input(B0));
pulseLength = get_timer1();
}
main()
{
delay_ms(1500);
while(1)
{
setup_ccp1(CCP_CAPTURE_RE); // Configure CCP1 to capture rise
setup_timer_1(T1_INTERNAL); // Start timer 1
enable_interrupts(INT_CCP1); // Setup interrupt on rising edge
enable_interrupts(GLOBAL);
if(pulseLength>1500)
{
output_high(A2);
delay_ms(1000);
output_low(A2);
}
else
output_low(A2);
}
} // end of main
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Thu Aug 11, 2005 2:09 pm |
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The data sheet says right here,
| Quote: | 9.1.3 SOFTWARE INTERRUPT
When the Capture mode is changed, a false capture
interrupt may be generated. The user should keep bit
CCP1IE (PIE1<2>) clear to avoid false interrupts and
should clear the flag bit, CCP1IF, following any such
change in operating mode. |
CCS has the clear_interrupt() function, specifically for this purpose.
You need to clear the INT_CCP1 interrupt before you enable
global interrupts.
Also, anytime a module behaves strangely, it's almost certainly
because of some quirky behavior that will be explained in the
data sheet section on that module. You should read it. |
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