modem communication

  • Thread starter Thread starter Ian Williamson
  • Start date Start date
I

Ian Williamson

Greetings,

I have searched endlessly on the news groups and have not
really found anything of substance regarding modem control
through rs232.

I have briefly looked at Richard Grier's CFSerial, but
have not been able to get it to talk with my modem.

Does anyone have some insight with regards to taking a
modem connected through the serial port, dialing a remote
location and then sending a file?

I could probably get this worked out in time, but I have
about 1.5 days to get this working.

Thanks in advance for any help.

Cheers, Ian Williamson
 
Hi Ian,

I don't recall, what problems are you having? Is this a standard modem
(using a hardware serial port), or is it a Bluetooth device? Your report is
the first that I've had that there was any problem communicating, though
there is an issue with parity that I haven't solved.

My DLL has worked with every device that I've tried it with, and I know that
there are hundreds of people using it, so I'd venture to guess that there is
some sort of configuration issue that is outside the scope of the DLL
itself.

I presume that you tried the simple terminal code that is part of the
download? If you simply check the Enable OnComm box, select your serial
port, click Open Port, and then type in the terminal window... You really
should see just the same thing as with any other terminal program. Do other
terminal programs work?

Dick

--
Richard Grier (Microsoft Visual Basic MVP)

See www.hardandsoftware.net for contact information.

Author of Visual Basic Programmer's Guide to Serial Communications, 3rd
Edition ISBN 1-890422-27-4 (391 pages) published February 2002.
 
Thanks for the replies.

Dick,

I have no doubt that your control works perfectly, I am
just having trouble getting it to work for me and due to
the nasty time constraints, I am needing some serious
hand holding to get this up and running.

I have an external Hayes compatible modem connected to a
serial port which is part of a docking station. This is
being run on a Psion Teklogix 7535 runing Win CE.NET
4.1. I open the port at 9600 baud and the CD, DSR, and
RI flags all return true. CTS is false (since I am not
clear to send, this would seem like a problem).

At this point (barring the CTS issue), I would hope that
I could just push "AT" commands through the port and the
modem would know what to do. Well, the modem does
nothing and this is where I am stymied. Hopefully it is
something simple, but this is my first adventure into
serial communications so I am quite lost.

Any advice?

Cheers, Ian
 
Hi,

Well, CTS should be True (not False). However, this is asserted by the
modem, not the WinCE system. Thus, this may be a clue. It "sounds" like
there may be a hardware problem. Are you sure that the cable is wired
correctly?

On the other hand, RI should be False (it only is True if the modem is
detecting an incoming phone call). Again, since it is True, I think there
may be some hardware issue here. DSR is True when the modem is powered up,
but... CD should be True only when the modem has connected with another
modem (though some modems always keep CD True, this is not usual). Again,
this also suggests a hardware issue.

Dick

--
Richard Grier (Microsoft Visual Basic MVP)

See www.hardandsoftware.net for contact information.

Author of Visual Basic Programmer's Guide to Serial Communications, 3rd
Edition ISBN 1-890422-27-4 (391 pages) published February 2002.
 
I tend to concur that there are some hardware issues.
This product has not yet been released to market and I
have already found some other issues with it. I have
spoken with their service people and they will be sending
the me their latest firmware.

Once I do get a stable serial connection, is it just a
matter of pushing strings to it? That is, once I open
the port, can I just send "ATDT#######" and the modem
will dial through? I imagine I will have to be listening
for the handshake and respond accordingly, but once I get
connected I think that will be enough of an impetus to
send me on my way.

Cheers, Ian
 
Hi,

Open the port... Then,

SerialPort.Output "ATxxxyyyzzz" & vbCr

You have to terminate the dial string (and all modem commands) with a CR
character. If you are using C#, then use char(13) instead of vbCr.
Naturally, in real code you would use a variable, not a literal.

Dick
--
Richard Grier (Microsoft Visual Basic MVP)


See www.hardandsoftware.net for contact information.

Author of Visual Basic Programmer's Guide to Serial Communications, 3rd
Edition ISBN 1-890422-27-4 (391 pages) published February 2002.
 
Thanks very much for your input on this matter Dick.

The vendor has asked for me to ship the unit back as they
are going to make some hardware and software fixes to it
following some problems I discovered with the unit. Upon
return I hope to make good use of your info.

Cheers, Ian
 
Hi Ian,

I don't remember if I asked... However, is this using the same port as would
be used for serial ActiveSync? If so, then you will need to use a
null-modem cable or adapter to connect to your modem.

Dick

--
Richard Grier (Microsoft Visual Basic MVP)

See www.hardandsoftware.net for contact information.

Author of Visual Basic Programmer's Guide to Serial Communications, 3rd
Edition ISBN 1-890422-27-4 (391 pages) published February 2002.
 
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