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000344_icurmtdude@yahoo.com_Sat Oct 25 12:16:00 2003.msg
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Path: newsmaster.cc.columbia.edu!panix!news.maxwell.syr.edu!postnews1.google.com!not-for-mail
From: icurmtdude@yahoo.com (icurmt)
Newsgroups: comp.protocols.kermit.misc
Subject: Re: DSR off ...
Date: 24 Oct 2003 17:55:13 -0700
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References: <cf6cc183.0310211334.2b68926b@posting.google.com> <slrnbpbcob.co2.fdc@sesame.cc.columbia.edu> <8ce22d01.0310211755.5aeb83f8@posting.google.com> <cf6cc183.0310221148.69ac828a@posting.google.com> <slrnbpdtri.ilh.fdc@sesame.cc.columbia.edu> <cf6cc183.0310230551.52867e2d@posting.google.com> <slrnbpg225.aad.fdc@sesame.cc.columbia.edu>
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Xref: newsmaster.cc.columbia.edu comp.protocols.kermit.misc:14597
Thanks Frank.
I figured it out. I took the port's file descriptor, ttyfd from the
kermit script passed it to my C program to toggle the DTR state.
Everything works fine now. Thanks for your timely inputs.
Ray
Frank da Cruz <fdc@columbia.edu> wrote in message news:<slrnbpg225.aad.fdc@sesame.cc.columbia.edu>...
> In article <cf6cc183.0310230551.52867e2d@posting.google.com>, icurmt wrote:
> : Alright, let me give you more insight to why I am seeing all these
> : problems. I am using the Single Board Computer to talk to the
> : Microcontroller unit through serial ports. The DTR pin on the SBC is
> : hacked to recycle the power on the MCU. Now when the communication is
> : initiated, the DTR pin goes high(1) which resets the MCU and
> : communication fails. Thats the reason that during "show comm"
> : I see that DSR is off. Now when the communication terminates, the DTR
> : is turned off (0) which turns the MCU on.
> :
> : Something which puzzles me is that why is DTR handshaking used here
> : even when I am stating in kermit program to use the Xon/Xoff
> : flowcontrol. I also tried the RTS/CTS handshaking but the result was
> : same.
> :
> DTR and flow control (usually) have nothing to do with each other.
> DTR is a signal from the computer to the modem saying "I am turned on"
> and/or "this serial port is open". By definition, when you turn it off,
> this supposed to break the connection.
>
> Unfortunately in this case, Kermit is not a general-purpose modem-control
> manipulating program. It operates at a higher level. "set line /dev/xxx"
> turns DTR on (and in most cases also RTS). Closing the device turns it off.
> RTS/CTS are used by the device driver (transparently to Kermit) for flow
> control if you have "set flow rts/cts".
>
> CD, CTS, DSR, and RI are incoming signals -- "read only". You can see
> them with "show comm" and you can test them with the WAIT command.
>
> The only way in Kermit that you can touch DTR is with the HANGUP command,
> which sets DTR low for about 250 milliseconds, then brings it back, which
> is how one tells a modem to hang up a telephone connection.
>
> - Frank