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On-Change Interrupt

 
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alwaysfresh



Joined: 04 Jul 2005
Posts: 8

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On-Change Interrupt
PostPosted: Tue Jul 12, 2005 12:28 pm     Reply with quote
My program goes into the PORTB on change interrupt service routine, #INT_RB, even though I can't see any signals changing on these ports. I am using the CDC-library of CCS to send data via USB to the PC, but I can't find where CDC may be interfering with portB. Any suggestions?...

I use to setup port b pin b4:

port_b_pullups(true);
set_tris_b(0x10);
enable_interrupts(INT_RB);

Thanks,
Andy
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Tue Jul 12, 2005 1:36 pm     Reply with quote
Do you mean that you get an INT_RB interrupt as soon as
you enable interrupts ?

If so, it's happening because you didn't clear the "change" condition
on Port B before you enabled interrupts.

You do this by reading port B.

Code:

#byte PortB = 6     // Address of Port B for the 16F series PICs

main()
{
char c;

port_b_pullups(true);
set_tris_b(0x10);
enable_interrupts(INT_RB);
c = PortB;    // Read PortB before enabling global interrupts.
enable_interrupts(GLOBAL);

while(1);
}
Mark



Joined: 07 Sep 2003
Posts: 2838
Location: Atlanta, GA

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PostPosted: Tue Jul 12, 2005 6:09 pm     Reply with quote
Read this->
http://www.ccsinfo.com/forum/viewtopic.php?t=23421&highlight=portb+output+interrupt
alwaysfresh



Joined: 04 Jul 2005
Posts: 8

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PostPosted: Wed Jul 13, 2005 7:47 am     Reply with quote
Works!... Thank you Mark your the best.

This morning I was starting to think the PIC's input at portB was broken or something. Safed again.


Andy
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