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'[PIC]: f628 intRC RS232 problems'
2002\04\03@031119 by Vasile Surducan

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A while ago someone ( Tony ? ) have mentioned problems in
sending data's on RS232 with F628.
I have the same problems, if I send ASCII by ASCII and not the same
character is ok, if I send the same ASCII twice the first one is ok, the
second one is garbage, the third is ok and so on...
I'm using 2400 bps 8,N,1 via an optoisolated RS232.
Any clue ?

best, Vasile

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2002\04\03@055106 by Larry Kayser

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>Vasile:

>Any clue ?

Yes, you have a code problem.  IF you have a timing problem (using the
internal RC oscillator which is at the edge of acceptable frequency range),
AND the second mutilated character follows the first good character
IMMEDIATELY, then what you can try is to add a little timing delay interval
to fix it.

I have ONE 628 PIC here that messes up occasionally on comms when using the
internal 4 MHz oscillator.  The really nasty part of ASYNC comms when it
messes up due to timing issues is that the test equipment to catch it is
both expensive and not at all common.

Larry
VA3LK

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2002\04\03@093603 by PY2NI

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   Bingo, Larry is right, I had the very same problem here, delay was used
to fix it and worked like a charm, obviously if you use a XTAL  it won't
happen.

Regards
Horta

73 Larry
de PY2NI

> >Vasile:
>
> >Any clue ?
>
> Yes, you have a code problem.  IF you have a timing problem (using the
> internal RC oscillator which is at the edge of acceptable frequency
range),
> AND the second mutilated character follows the first good character
> IMMEDIATELY, then what you can try is to add a little timing delay
interval
> to fix it.
>
> I have ONE 628 PIC here that messes up occasionally on comms when using
the
{Quote hidden}

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2002\04\03@120602 by Thomas McGahee

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Make sure the transmitting end gives sufficient pause
between characters so that receiving end can receive
and store/process character before next one comes in.

It is best to build this extra stop bit delay into the
serial transmit routine.

Someone had emailed me about a similar problem earlier.
They thought it might be a problem with my picuart.asm,
but it is actually a problem of methodology, as only
the USER knows what is a REASONABLE delay for THEM
in their particular application.

Fr. Thomas McGahee

{Original Message removed}

2002\04\03@174429 by Tony Nixon

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Vasile Surducan wrote:
>
> A while ago someone ( Tony ? ) have mentioned problems in
> sending data's on RS232 with F628.
> I have the same problems, if I send ASCII by ASCII and not the same
> character is ok, if I send the same ASCII twice the first one is ok, the
> second one is garbage, the third is ok and so on...
> I'm using 2400 bps 8,N,1 via an optoisolated RS232.
> Any clue ?
>

I don't think the int osc is all that great for RS232 comms, but it can
work if you don't need super fast transfers.

I usually transfer like this..byte-ACK-byte-ACK-byte-etc

If you have long stop bits then the same result may be achieved.

I guess this minimses the chance of errors given the tolerance of the
oscillator.

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Tony

mICros
http://www.bubblesoftonline.com
spam_OUTsalesTakeThisOuTspambubblesoftonline.com

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