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Connecting a RS232 device to GPRS

I have a PLC with a RS232 connection this PLC are connected to the internet via a ADSL cable connection and with a converter from TCP/IP to RS232 is it possible to establish a terminal connection
The converters take what comes in on the telnetport 23 stripe it for the TCP/IP headers and send the rest of telegrams out on the converters RS232 port to the PLC

What I now want is to make this connection via GPRS, I have found an bought a Simens MC35 modem which have the capability to connect to the GPRS net, but I think that the modem is without a TCP/IP stack, and I therefore need some hardware to set in between the modems RS232 port and the PLCs RS232.

Is there any body here who knows how this can be done


Best regards
/Morten
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msconsult
Asked:
msconsult
3 Solutions
 
MeffCommented:
You can save the money for external components if you use a GSM modem / module that comes with embedded protocol stack "eay GPRS" like listed on http://www.gsm-modem.de/gprs-tcp-ip.html
A GPRS module / modem with its EASY GPRS feature can be seen as a special device, embedding and controlling the PPP/(UDP)TCP/IP protocol stack inside itself. In this way the Localhost sees a "virtual serial line" connection with the application software on the Server machine.
Differently from other GPRS devices that embed the TCP/IP protocol stack; an EASY GPRS device does not provide a set of API functions to interface with the protocol stack but it automatically manages it internally as specified when starting the connection. This completely relieves the designer from TCP/IP managing and knowledge. The connection through the internet with a remote host Application layer residing on the server can be done as easily as a CSD data call, by following the steps:  

With an AT Command set the GPRS context 1 properties (to allow the GPRS modem to activate later the GPRS connection to internet on demand);
With an AT Command set the Authentication parameters (UserID and Password) to be used later during the authentication process on the GPRS network
With an AT Command define the host by setting the remote host port to be contacted and with which transport protocol (TCP or UDP). There are three things to configure:
 Transport layer protocol to be used: TCP or UDP
 Server IP address or name (resolved with a DNS query automatically by themodem)
 Server Port to be contacted
Start the connection with the server with a proprietary "internet dial" command. When the device receives the CONNECT indication, then it's directly exchanging data with the remote host server Application Layer.  
Regards
Meff

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SimonTayCommented:
Or you can use the iConnector - as on http://www.tdc.co.uk/modems/modem_tcpip_connect1.htm#iconnector, this sits in between your application and the MC35T, and intercepts additional AT commands understood by the iConnector.

Very simple to use, with full TCP/IP, POP, Web server etc.etc.

Simon
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drelectroCommented:
Or a complete product like the UltraLite iT from
http://www.call-direct.com.au/gsm-gprs_modems.htm
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