New YAPP 2 of 2 - Converter for NMEA 0183 from 38400 to 4800 baud

[Andrew G]

Once again gauging interest - this time in a YAPP that takes NMEA0183 transmitted at 38,400 baud (eg an AIS) and slooooooooooows it down to 4,800 so that it can be used as input to slower instruments. (I believe that I can work around it for my setup but I'm checking others' interest). It arose when my main GPS died but I couldn't use the AIS one because it was set to 38,400 for OpenCPN. I was time-challenged and didn't have the time to reconfigure my system -midnight in a dodgey spot. I ended up using a spare handheld GPS at 4,800.
Initial specs:
- self powered? or off some other circuit?
- default to pass through as many GPS location sentences as possible but possibly configurable
- RS232 ( eg DB9) in and out
Any interest (and who might do it)?
Andrew

 

[Cardo]

We have a couple of items on our boat that do this, though probably not quite what you're after:

Our Raymarine AIS has 38400 and 4800 in/outs. Anything received on the 4800 in is output on the 38400, and vice versa.

We also have a Raspberry Pi running Laika's fantastic Kplex. This is a great multiplexer. We have 4800 and 38400 inputs/outputs that are multiplexed and also pushed out to our wireless network for OpenCPN (and others) to use.

I'm also contemplating adding the bilge pump (and other things) sensing to the Pi so we can keep an eye on stuff from afar.

 

[AngusMcDoon]

Once again gauging interest - this time in a YAPP that takes NMEA0183 transmitted at 38,400 baud (eg an AIS) and slooooooooooows it down to 4,800 so that it can be used as input to slower instruments.

A rate down changer will not really work. The reason why AIS runs at the faster rate is because there is much more data to send. Slowing it down by a factor of 8 means that if more than a few ships are in range then most of the data will have to be discarded. There is a YAPP coming that is a 3-1 multiplexer and can also be configured to change the rate up, but not down. It would be an easy software modification to change the rate down if you want to try it, but I don't hold out much hope that it will be useful.

 

[Andrew G]

I would use the AIS' 38400 via USB for AIS data - I am only looking for basic GPS data at 4800 (RMC etc) it doesn't matter if it skips a few - a yacht isn't going to move too far between sentences. Andrew

 

[AngusMcDoon]

I would use the AIS' 38400 via USB for AIS data - I am only looking for basic GPS data at 4800 (RMC etc) it doesn't matter if it skips a few - a yacht isn't going to move too far between sentences. Andrew

The forthcoming YAPP will do the job with a couple of lines changed in the software. You won't lose any GPS data as that fits into 4800 baud. It's only AIS that doesn't.

 

[Andrew G]

As I've said before "you're the Man". Andrew

 

[Birdseye]

Once again gauging interest - this time in a YAPP that takes NMEA0183 transmitted at 38,400 baud (eg an AIS) and slooooooooooows it down to 4,800 so that it can be used as input to slower instruments. (I believe that I can work around it for my setup but I'm checking others' interest). It arose when my main GPS died but I couldn't use the AIS one because it was set to 38,400 for OpenCPN. I was time-challenged and didn't have the time to reconfigure my system -midnight in a dodgey spot. I ended up using a spare handheld GPS at 4,800.
Initial specs:
- self powered? or off some other circuit?
- default to pass through as many GPS location sentences as possible but possibly configurable
- RS232 ( eg DB9) in and out
Any interest (and who might do it)?
Andrew

You would get interest from owners of old raymarine c80 plotters like mine where the nmea input / output has to be one speed or the other so you cant feed the VHF and take an AIS signal at the same time. but presumably that would also require some sort of mixing facility

 

[prv]

You would get interest from owners of old raymarine c80 plotters like mine where the nmea input / output has to be one speed or the other so you cant feed the VHF and take an AIS signal at the same time. but presumably that would also require some sort of mixing facility

I think the existing YAPP that provides power and connections for a BR355 GPS is a better solution to that problem.

Pete

 

[st599]

That can only ever work for a pretty sparsely populated stream. You'll need a pretty large FIFO to deal with bursts.

 

[nigelmercier]

A rate down changer will not really work...

Quite so.

You need to get a copyright on the name