2019-05-25, 10:14 PM
(2019-05-25, 09:11 PM)skyeyedoc Wrote: Thanks for replying! I feel like I'm on the right track now. The Standard Horizon vhf should be a slam-dunk if you're right about the RS-485/RS-422 protocol being the way to go.
If I'm understanding correctly, because this radio only wants to accept gps sentences, and the wiring is only two strands, it must be half-duplex. If that is the case, what do you think about this CH340T based dongle, at less than half the price.
If this works for the OP to vhf link, I'm going to try it to link OP to an old Raymarine autohelm radio navigation interface next. I'm much less certain of making that work, for lack of clarity on just what sentences to direct to it. (See my post from yesterday).
Which raises another question in my mind: It looks like RS485 can connect a number of devices in parallel? Does that mean I could tap this same dongle in parallel to tie in that radio interface? The autohelm interface is also receive only, and I believe it only responds to cross-track error sentences (dead-reckoning, not measured). So, it, too, should work in half-duplex.
So much to learn!
What do you think? Thanks again for your help.
Hi,
according to NMEA0183 specs, one talker can speak to 4 listeners, so theoretically yes, you can wire the autohelm in parallel to your vhf. But you can have finer control over sentences when you have separate output to everyone.
I used the specs to have the GPS-mouse speak directly in parallel to the vhf and OP, so even if OP is not running for whatever reason, the vhf still has gps-data for distress calling...
with USB-RS422 converters just beware: I once had one (a cheap one) which gave interference on ch 16 of the vhf - and only on ch 16. Not good when you are boating. Took me some time to figure out, which element gave the noise on the vhf.
just my 2cts
fair winds
Christian