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post #3 of Old 01-03-2011 Thread Starter
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Originally Posted by BarryL View Post

I don't think you can do what you want to. AFAIK, the reason is that the AIS port runs at 38.4K baud and the DSC port runs at 4800 (or maybe 9600?) baud.

You will need two serial ports, 1 at 38.4 to receive the AIS data from the SH radio and another at 4800 baud to send the GPS position data from the computer to the SH radio.

The serial ports can be real or virtual. If virtual, you will need two USB connections.

Good luck,
Thanks for the reminder about baud rate differences. The newly announced GX2150 addresses this by allowing you to set AIS and DSC outputs to the same baud rate. There's another thread where they are saying that this allows the AIS and bidirectional DSC communications to go over a single port. In other words, GPS coordinates go out to the radio, and both AIS and DSC sentences go from the radio to the chart plotter or netbook (in the case of OpenCPN). But the main challenge seems to be configuring OpenCPN to allow both GPS out and AIS in via the same COM port. I still have more to learn, but it looks like there might be serial port emulator software that can duplicate COMx port to COMy, thus tricking the software into thinking the AIS is coming in on a different port. I'm going to need to get the GX2150 hardware first and start to experiment with it to see if if works.

This is only a major issue if I try to do Bluetooth from radio to netbook, because the serial to Bluetooth adapters are so expensive ($50-100 per port) that I would want to minimize the number of COM ports. If I instead make a hardwire connection I can afford to split things up over multiple COM ports because serial to USB connectors are very inexpensive (<$10) and I can use a hub to aggregate them all into one USB wire going to the cockpit. (Yes, I plan to mount my netbook in the cockpit, since I'm a daysailor who picks my conditions carefully. I sailed all season last year without a drop of water getting into the cockpit.)

Rick S., Swarthmore, PA
USCG Certified Captain, 50 Ton Master and OUPV
ASA Certified 101/103/104/105/106

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2001 Catalina 34MkII Tall Rig Breakin' Away, Universal Diesel M35B, Mantus 35 lb. anchor, sailing out of Rock Hall Landing Marina

Last edited by TakeFive; 01-03-2011 at 02:50 PM.
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