Chartplotter to Tillerpilot interface

Joe · Apr 2, 2012

Isn't there a "hub" device available from Garmin? Or at least a protocol that would set up a "through" signal to the repeater? I don't have the system but always thought it could be set up as such.

Tim R. · Apr 2, 2012

Check out Brookhouseonline.com. They sell NEMA 0183 combiners and multiplexers. Or you could purchase the dedicated display for the wind instrument, then there would be no need to connect it to a CP.

Bill Roosa · Apr 2, 2012

Hey FourPoints, Please don't take this as flippant. You said you are planning future upgrades. Save yourself some $$$ and headache. Begin with the end in mind.

SeaTalk is not compatible with anything but SeaTalk (Raymarine)
NMEA is a one talker and many listener type circuit so your two NMEA chart plotter circuits are probably a talker and listener. Don’t expect to get anything out of the listener it only listens. With that said you would need 3 NMEA talkers wind, plotter and AP. That is unless the chart plotter repeats on its talker what it hears on its listener circuit (a lot do this BTW but you need a comms program to check the data streams as it is never in the documentation). In that case you can use the wind talker to the chart plotter listener and the chart plotter talker to the AP listener and the AP talker to the chart plotter listener (duel feeds to chart plotter listener circuit)(yes Martha there will be data crashes and that is ok).
Which is why you should go with ONE component manufacturer for all your boating instruments and not a hod-podge of suppliers.
I just connect everything to the SeaTalk data/power buss and it works
But you probably save money right up till the time you have to buy that data multiplexer to tie it all together.
Begin with the end in mind

Bill Roosa · Apr 3, 2012

SeaTalk is a simply two wire IEEE interface that MAY be the same interface as the CANet from an electrical and protocol standpoint. ie + - 5 volts for mark and space, listens to its on output if garbled stops and waits a random time with more important items (GPS) waiting less and less important items (water temp) waiting more time, .....
But the format of the sentences is most assuredly not the same so one speaks English and the other Chinese but both use air, sound and vocal cords to us an analogy. You could probably network (share the wires) the two types but only seatalk would respond to seatalk and CANet to CANet.
You can have as many listeners on a NMEA circuit as you like as long as what they are listening for is supplied on that circuit. Yes your repeater would work fine listening to your chart plotter.
NMEA is really simple but it takes some understanding of how each piece handles the data to and from it to develop a working system.
I'd recommend you get some paper and make a list of each talkers sentences that it can broadcast on its talker circuit. Then draw an arrow to the unit that needs that sentence to operate. That will pretty much define which items need to be connected. In most cases the sensors are talkers and that is the sticking point as you can't put 2 or more sensors on the chart plotter’s one listener circuit so you can never get all your sensor data to the chart plotter.
The other way to do this (and the way NMEA was intended to work) is ALL items have one talker and one listener circuit. ALL items append their sentences to the data coming in on their listener circuit. Then all you have to do is daisy-chain the items (talker to listener) in one circuit
[wind]talker-->listener[depth]talker-->listener[speed]talker-->listener[gps]talker-->listener1[chart plotter]talker--listener[AP]talker-->listener2[chart plotter]
note the listener1 and 2 on the chart plotter so the AP can do it's reporting.
But you have to understand what info each unit needs so that you build the daisy chain in the right order. The question then becomes: Does the AP need to talk to the chart plotter so the chart plotter has all the info it needs to keep the AP on course? Since you don’t have two listeners at the chart plotter and most sensors manufacturers don’t want you buying other folks products and so do not give you both a talker and listener circuit and don’t append the listener data to the talker data…….
It is just much easier and cheaper (the manufacturers are not stupid but do have kids to put through college) to just go with one manufacturer and their proprietary data network.

On your last question; no you cannot connect all the talkers on to the chart plotters one listener circuit. That would be placing more than one talker on a circuit and you will get data crashes as the to get into a shouting match. That is the textbook answer. The NMEA wind sentences are lower priority and don’t get transmitted as often as a NMEA GPS sentence. So if you are willing to suffer some reduced and possibly odd behavior then I’d say try it and see. The worst that can happen is it does not work which leaves you right back where you started except now you own the instruments and can’t network them without the magical black box.

It is just easier to stick with one guys products.