At 12:46 24/05/98 EDT, you wrote:
>Hi everyone
>
>I hace a project where a stamp BS2 and a Pic16F84 are talking back and forth
>on the same board (about an inch apart). The code utilizes 9600 baud. I
have a
>couple of questions.
>
>1) For 9600 baud and bit timing should be 104us. The best I have been able to
>do in my 16F84 program is 116us between bits, due to the way I have
>implemented the code. This  is consistent for both the serout and serin
>routines. Can I communicate effectively with the BS2 with the slight
offset in
>timing? The BS2 will utilize its standard serin/out commands.
>
>2) What kind of limitations do I have for baud rate in this application?
Can I
>run at 19,200 or even higher?

I just replied to your later message.

If you're doing this in software (or hardware for that matter) I always aim
for an error of less than 1%, and I try to get the best I possibly can
especially when using equipment with different UARTs or unknown UARTs.

For a software implementation, check for the start bit periodically (or
have it interrupt driven) then start a (software or hardware) timer for
half the bit time. Resample the start bit if valid, start a counter for one
bit time (then you'll be in the middle of bit 0 (lsb comes first of
course), repeat 5/6/7/8 times (or 1 more than each of these if you have a
parity bit).

As a "slight cheat" I sample about 1/4 after the bit transition time since
I am using a software implementation with various polling delays within the
start bite period time.

Regards

Adrian

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