I'm not sure if the modem uses the handshaking to determine R/Tx changeover.
The PC software will just be the datalogger client software.  I'm using a
World Wireless Communications 900 SS Direct system.  It is rated at 35+
miles, 4800/9600 bps.

Dave

---------------------
You could perhaps get it working without the PIC by looping back
the RS232 handshake lines so your modem thinks it's allways OK
to send data. I'm no expert on this, usually I find a diagram for a null
modem cable and work it out from there. One thing to watch out for
though is that the modem may use the handshaking lines to
determine Rx/Tx changeover if it uses a half duplex RF link.

To use the PIC as a buffer then you'll need a little memory of
course. If datalogger dumps at 4800 baud and radio modems work
at 9600 then a buffer in internal RAM would be sufficient. If you are
wiriting the PC software you could get some software handhshaking
going on with the PIC so that it retries in case of corruption to
guarantee the data from the logger is received without error (unless
the wireless telemetry system already does that for you.) Buffer
would be a problem again as there is no handshaking with the
datalogger.

BTW, I'm intereseted in what wireless devices you are using, as I'm
looking for a cheap off the shelf setup for low speed 200-300m
without any fancy stuff.

Brent Brown
Electronic Design Solutions
16 English Street
Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/text: 025 334 069
eMail:  brent.brown@clear.net.nz

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