Hi,

I'm trying to set up NMEA-0183 "network" on my boat. I've a Globalsat BU-353 GPS puck that connects to my Netbook with Ubuntu Jaunty over an USB port. Works fine so far.

Now I want to forward NMEA sentences to my VHF-radio which has an NMEA input:

0--------------GPS+

0-------------GPS GND

To get the signal to the GPS i guess I'll need an USB to serial converter (the Netbook doesn't have a serial port), writing the NMEA strings to the USB port and connect the serial line to the VHF GPS-pins, Am I right?

Has anyone tried this before? I've heard that one should use opto-couplers when connecting NMEA devices, is this necessary when running all equipment on the same 12v system?

Someone who has this working or can point me in the right direction would be very appreciated!

Should not be necessary to isolate RS-232. However it could possibly protect the netbook if the VHF radio was ever hit by lightning.

I assume that your receiver already acts as a USB serial adapter /dev/ttyUSB0. Obviously the new USB serial port adapter will be /dev/ttyUSB1. You would want to use some udev rules so that each physical device will automatically be the same device ID. This will make programming much easier. Basically you need to forward all serial data from one port to the other. Connect the TX and GND of the serial port adapter to the VHF radio GPS+ and gnd pins respectively. NMEA data is slow i.e. 4800 baud so you should not have any major problems.