The transmission is from PIC to PIC - one USART to another.  The sending PIC
is a 16F627.  The scope readings show perfect 5V signals at 9600 baud.
There is no parity bit, only 8 data bits, plus start and stop bit.

Jen

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Martin Peach
> Sent: Wednesday, January 23, 2002 1:09 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: PIC18 USART RX Data Corruption
>
>
> ----- Original Message -----
> From: "Jennifer Loiacono" <jen@AUTO-SERV.COM>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Wednesday, January 23, 2002 12:35 PM
> Subject: [PIC]: PIC18 USART RX Data Corruption
>
>
> > Jennifer Loiacono
> > President
> > Automaton Engineering, Inc.
> > P.O. Box 10282
> > Brooksville, FL 34603When receiving serial data on the
> PIC18C442, the
> value
> > is not reflected correctly in the RCREG reception register.
>  However, the
> > signal on the receiving PIC is perfect in terms of timing
> and accuracy.
> > Despite accurate signal levels, debugging RCREG immediately
> after data is
> > received reveals that the byte seems to flip back and forth.
> >
> > e.g., a byte equal to 4 (dec) will oscillate between 4 and
> 32.  A byte
> equal
> > to 1 will oscillate between 1 and 128, etc.
> >
> > Again, this value is being read immediately after reception
> (triggered by
> RX
> > interrupt), so it is highly unlikely that program code
> could be altering
> the
> > register after reception.
> >
> > Has anyone seen a problem like this before, or perhaps have
> any ideas as
> to
> > its cause?  I have been stumped on this for a while, so ANY
> help would be
> > greatly appreciated!
>
> It usually happens when the serial data is not in the right
> form before it
> hits the PIC pin (wrong voltage levels, skewed pulses, parity bit
> mismatch...): where is it coming from? Straight from a PC
> port? From an
> optocoupler? from a rf receiver? Need more info.
>
> /\/\/\/*=Martin
>
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