Anybody with NMEA knowledge?

GraemeS

GraemeS

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If any kind sole has time, would you have a look to see if this NMEA scheme will work. View attachment 48601

I have not tried it yet but would like to know in principle whether it will work. The end goal is to connect to a pc via USB connector to run on Opencpn.

I hope to start wiring this in at the weekend!

Many thanks Graeme
 
GraemeS said:
If any kind sole has time, would you have a look to see if this NMEA scheme will work. View attachment 48601

I have not tried it yet but would like to know in principle whether it will work. The end goal is to connect to a pc via USB connector to run on Opencpn.

I hope to start wiring this in at the weekend!

Many thanks Graeme
Click to expand...

Honest answer: it might or it might not - I couldn't be bothered to work out which wire went where. You clearly have a surfeit of red and black cable.

You'd be better off with shielded cable anyway for anything other than short runs (no need to get stuff stamped NMEA at great expense - simple multi-cored cable with a shield from Amazon or elsewhere will do - has the added bonus that each core will have a different colour).

Having different coloured cables will also help you when you come to fault-find or modify it in a year or two's time.
 
Not sure

You seem to be freely mixing speeds ( vhf feeds AIS ) but unless they are compatible ports one doesn't know.

Make the NMEA signal wires a different colour and/ or leave out the power wires on the diagram!

Take the GPS output and multi drop it to the AIS ( if it wants 4800 baud ) and the VHF rather than daisy chain it, then if the VHF is off / broken you don't lose both. Consider this approach elsewhere. ie. Use the Yapp NMEA out to drive several inputs instead.

Does the seatalk to NMEA bridge accept 19k2 in? The AIS is feeding it and I'm pretty sure it will be sending it's data faster than 4800. ( I looked at the raymarine manual and couldn't see anything abut speeds )

Many ways to skin the cat!
 
Thanks to you all so far.

I will have a closer look at http://maretron.com/ but it appears to be for NMEA 2000 rather than NMEA 0183 however I'm not sure what the wiring differences are if any.

Nimbusgb I wasn't certain that you can do multi-drops. I will have another look at that. The AIS outputs at the higher speed but as I understand it the YAPP unit will take that higher speed and drop the speed out on the RS232.

The AIS has both 4.8 and 38.4 speed so its the 4.8 supplying the seatalk.

Colour of wiring is only to indicate +/- leads but I can change them and yes it would have been better to leave the power supply out.

I do appreciate the responses, so thank you.

Graeme
 
nimbusgb said:
Not sure

You seem to be freely mixing speeds ( vhf feeds AIS ) but unless they are compatible ports one doesn't know.

Make the NMEA signal wires a different colour and/ or leave out the power wires on the diagram!

Take the GPS output and multi drop it to the AIS ( if it wants 4800 baud ) and the VHF rather than daisy chain it, then if the VHF is off / broken you don't lose both. Consider this approach elsewhere. ie. Use the Yapp NMEA out to drive several inputs instead.

Does the seatalk to NMEA bridge accept 19k2 in? The AIS is feeding it and I'm pretty sure it will be sending it's data faster than 4800. ( I looked at the raymarine manual and couldn't see anything abut speeds )

Many ways to skin the cat!
Click to expand...

yes I agree, avoid daisy chaining and watch the baud rates.

Also watch out for trying to send too much data via the yapp. I believe it doesn't buffer it so you could find it drops some sentences probably in a random order.

More sophisticated multiplexers like the Shipmodul USB offer the ability to prioritise messages and also filter out duplicate sentences, at a price of course.
 
NMEA 2000 and 0182/3 are completely incompatible on the same wires.

Be careful of what you request of any interface dropping speeds from 19k2 (or above ) to 4800. The whole reason they went faster is that they ran out of time between 1 second updates. Unless the Yapp is filtering sentences you could flood the data output which would make your autopilot battle to keep a gps track. Rather get 4800 baud, clean GPS data to it directly. You may be trying to get a gallon into a pint pot with resultant lost bits and overrun data sentences.

Oops - fingers too slow! :)
 
I think it works from a speed matching perspective. Question I'd ask is whether the VHF repeats its NMEA input along with adding DSC/DSE sentences or if the NMEA out is DSE/DSC only (thus scuppering the GPS repeating plan).

Looks like you couldn't send stuff to the autopilot with OpenCPN with this set-up.

When planning this sort of stuff I think it's valuable to first of all start with an idea of what combinations of stuff are regularly on together, then make a list of what you want to be able to talk to what in your "normal" sailing circumstances. For example assuming your VHF *does* repeat the GPS (do check that) having the system rely on the VHF being on for GPS availability wouldn't bother me but might bother people who want GPS when the radio is off. I normally sail with my AIS turned off so I wouldn't want to rely on that being on to feed GPS data to the VHF.
 
GraemeS said:
Colour of wiring is only to indicate +/- leads but I can change them and yes it would have been better to leave the power supply out.
Click to expand...

Power supply would be OK left in providing that was the only red & black wiring.

Just make the NMEA wiring different colours.
 
Surely you want the YAPP NMEA output going to the Seatalk box NMEA input?

Go back a stage and think as ports instead of wires, draw a diagram with arrows showing data flow.

Other than that, your scheme depends on the AIS passing out the GPS data from the VHF along with its own.
May work, I have not read TFM.

Should there be a data path from the AIS to the VHF? (e.g. for the VHF to call up MMSI numbers RX'd by the AIS?)
 
All this information is great. I'm going to spend the evening having another look. I'm not too bothered about the autopilot getting gps data but I will want wind data to the autopilot. I'd also want the ais switched off most of the time so will have to look at the implications of some equipment not running all the time. Most of the time I wont have the PC working either but I think AIS as an aid at night will be useful.

I might re do the drawing and perhaps re-post tomorrow.
 
GraemeS said:
All this information is great. I'm going to spend the evening having another look. I'm not too bothered about the autopilot getting gps data but I will want wind data to the autopilot. I'd also want the ais switched off most of the time so will have to look at the implications of some equipment not running all the time. Most of the time I wont have the PC working either but I think AIS as an aid at night will be useful.

I might re do the drawing and perhaps re-post tomorrow.
Click to expand...

You might consider fitting a switch or 2 so you can change the data source to give more flexibility.
 
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