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Unwanted Echo — Parallax Forums

Unwanted Echo

ArchiverArchiver Posts: 46,084
edited 2001-03-02 03:44 in General Discussion
I am using the Basic Stamp 2 on the Board of Education. When I send
it a text string with SERIN, it echos that string in front of
whatever string I have it responed with using SEROUT.

Running this....

loop:
SERIN 16, 16780, [noparse][[/noparse]WAIT("LineId")]
SEROUT 16, 16780, [noparse][[/noparse]" _Line ID received_ "]
GOTO loop

...gives me
LineId _Line ID received_

instead of just
_Line ID received_

I would like to just see the response '_Line ID recieved_' from the
output.

Anyone know why this is and how to fix it?

This problem tends to threaten the usefulness of the Stamp for my
project.

Thanks,
Martin

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2001-03-02 03:44
    This is normal because of the way the Stamp "steals" -12V from the PC. If
    you look at the schematic, the RX and TX line are more or less shorted
    together. This limits port 16 to half duplex. There is no real solution
    except to use a port other than port 16 (which means a MAX232/232A/233 for
    +/- voltage conversion). You can read about this in the Stamp FAQ
    http://www.al-williams.com/wd5gnr/stampfaq.htm

    Regards,

    Al Williams
    AWC
    * Floating point math for the Stamp, PIC, SX, or any microcontroller:
    http://www.al-williams.com/awce/pak1.htm


    >
    Original Message
    >>
    > I would like to just see the response '_Line ID recieved_' from the
    > output.
    >
    > Anyone know why this is and how to fix it?
    >
    > This problem tends to threaten the usefulness of the Stamp for my
    > project.
    >
    > Thanks,
    > Martin
    >
    >
    >
    >
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