auto-tune serial port

23 May 2006 8:24 AM

SteveR

I've been looking at some applications that auto-tune the serial port
settings as a stream of data is sent to it. I want to add this type of
function in my software but I can't find any sample code to suggest how I
should start to do this. Does anyone know how this works? Do you tune the
baudrate first and then databits, handshaking etc?

--
Steve

23 May 2006 3:51 PM

Dick Grier

Hi,

I have example code in my book. Basically what I do is to Open the port at
the highest possible speed (typically 115200 bps), with 8-data bits and No
parity. I then wait to see if there are any errors (Framing, Parity, Break,
or Overrun). If there are, I assume this is not the correct set of
parameters. I close the port, change the parity (to E or O), then repeat.
After I've tested each parity setting, I change the number of bits (I only
test for 7-bit or 8-bit data). If I still get an error, I reduce the speed
to the next lower setting (57600 bps) and repeat all of the previous
tests -- I continue to repeat these steps until I have no errors BUT do
receive some sort of data. Naturally, if there is no receive data -- even
if there is no error, you haven't arrived at an "answer."

This works most of the time. It can be fairly slow, because you have to
wait a couple of seconds after you have opened the port (if no error is
generated), to make sure that, in fact, there is data present.

Dick

--
Richard Grier, MVP
Hard & Software
Author of Visual Basic Programmer's Guide to Serial Communications, Fourth
Edition,
ISBN 1-890422-28-2 (391 pages, includes CD-ROM). July 2004, Revised March
2006.
See www.hardandsoftware.net for details and contact information.

24 May 2006 6:27 AM

SteveR

Thanks Dick. I ordered your book straight away!

--
Steve

Show quote

"Dick Grier" wrote:

> Hi,
>
> I have example code in my book. Basically what I do is to Open the port at
> the highest possible speed (typically 115200 bps), with 8-data bits and No
> parity. I then wait to see if there are any errors (Framing, Parity, Break,
> or Overrun). If there are, I assume this is not the correct set of
> parameters. I close the port, change the parity (to E or O), then repeat.
> After I've tested each parity setting, I change the number of bits (I only
> test for 7-bit or 8-bit data). If I still get an error, I reduce the speed
> to the next lower setting (57600 bps) and repeat all of the previous
> tests -- I continue to repeat these steps until I have no errors BUT do
> receive some sort of data. Naturally, if there is no receive data -- even
> if there is no error, you haven't arrived at an "answer."
>
> This works most of the time. It can be fairly slow, because you have to
> wait a couple of seconds after you have opened the port (if no error is
> generated), to make sure that, in fact, there is data present.
>
> Dick
>
> --
> Richard Grier, MVP
> Hard & Software
> Author of Visual Basic Programmer's Guide to Serial Communications, Fourth
> Edition,
> ISBN 1-890422-28-2 (391 pages, includes CD-ROM). July 2004, Revised March
> 2006.
> See www.hardandsoftware.net for details and contact information.
>
>
>