Hi Neil

Well that makes/made sense to me...........till I read the data sheet and on
page 94 in the interrupts section it says that reading the RCREG receive
buffer clears PIR3.RC2IF interrupt flag bit.

I originally planned to clear the bit and I suspected the same thing so I
tried clearing the flag in the first line of my ISR.

It makes no difference if I don't have the section that clears the over run
error then I stop getting interrupts after two characters/interrupts.

I can't understand what is magic about two if that is not the reason or why
an over run should stop the UART from going on with its life.
Why does in not throw an error and then clear the error on the next good
character?
I thought the over run and framing error was just a check to see if the byte
was good.

On my other port I never check for any errors.
I expect errors and make my parser able enough that if my string/buffer does
make sense I just throw away the bad byte/message and move on with things.
If it were locking up like this one I would be hung up all the time just by
plugging and unplugging the cable in the middle of things but that has no
effect on the first serial port/its ISR.

I do suspect if I knew why this happens I could put the thing high.

void handle_chars_gps(void)
{

  PIR3bits.RC2IF = 0;                     //reading a char is supposed to
clear the interrupt flag so I should not need to do this either way this
makes no difference 

 if (RCSTA2bits.OERR) 
 {   
  RCSTA2bits.CREN = 0;                       //disable then enable the
receiver to clear the over run error
  RCSTA2bits.CREN = 1;                       //if I don't do this I only get
two interrupts and then they just stop
  return;
  }                      
 char_holder = getc2USART();                      //this causes problems
even with out pushing the the character to the buffer if I make the thing a
high priority

 Thanks again for the help
 
 
 
Phillip
Things should be as simple as possible but no simpler
 
 
 
Phillip Coiner
CTO, GPS Source, Inc.
 
 
Your source for quality GNSS Networking Solutions and Design Services, Now!

-----Original Message-----
From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of
Neil Baylis
Sent: Tuesday, September 19, 2006 9:52 AM
To: Microcontroller discussion list - Public.
Subject: Re: RE: RE: FW: [PIC] Trouble getting my ISR high

Phillip,

 RCSTA2bits.CREN = 0;    //disable then enable the receiver to clear the
over run error
 RCSTA2bits.CREN = 1;        //if I don't do this I only get two interrupts
and then they just stop

The two interrupts would be:

1, an interrupt for receiving a character.
2, an overrun interrupt.

Is that correct? If so, it means you're not clearing the interrupts
correctly. When the second character arrives, the uart thinks you
haven't read the first one, so it posts the overrun error.

Neil
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