NMEA port sharing

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JimC

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I know that one speaker can address several listeners, but can two speakers address one listener? e.g. vhf radio and AIS receiver both outputting to single input port on chart plotter.
 
So do all talkers speak to the multiplexer and then it becomes the single talker to everyone else but combining all the messages? NMEA is a slowly opening book for me.
 
Lazy Kipper said:
So do all talkers speak to the multiplexer and then it becomes the single talker to everyone else but combining all the messages? NMEA is a slowly opening book for me.
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Sort of, the multiplexer effectively sorts the different NMEA messages into an orderly stream, so that they don't clash with each other. Multiplexers might also change the data speed (baud rate) of the messages - AIS data for example runs at a higher speed than most other NMEA messages.
 
@AngusMcDoon Is there a PIC with multiple UARTs that would be suitable for a YAPP?
I did try searching but the noise to signal ratio is high
 
AndyJ76 said:
@AngusMcDoon Is there a PIC with multiple UARTs that would be suitable for a YAPP?
I did try searching but the noise to signal ratio is high
Click to expand...

There are quite a few with 2 and 1 or 2 more could be simulated in software at 4800 baud, i.e. 18F26K22. Alternatively the STM32F100RB Discovery board for £8 has 3 and could easily handle 2 more in software.
 
JimC said:
I know that one speaker can address several listeners, but can two speakers address one listener? e.g. vhf radio and AIS receiver both outputting to single input port on chart plotter.
Click to expand...

May be a stupid question (and I'm a bit of a duffer, anyway), but what is outputting from the vhf to the plotter? I have the situation on outputting the plotter NMEA sentences to the vhf for DSC, and would like to output AIS from the vhf to the plotter, but the plotter doesn't read VDM sentences, unfortunately. I'm trying to think of a situation of two outputs to a single device? Radar and AIS to the plotter! anything else?
 
Neil said:
May be a stupid question (and I'm a bit of a duffer, anyway), but what is outputting from the vhf to the plotter? I have the situation on outputting the plotter NMEA sentences to the vhf for DSC, and would like to output AIS from the vhf to the plotter, but the plotter doesn't read VDM sentences, unfortunately. I'm trying to think of a situation of two outputs to a single device? Radar and AIS to the plotter! anything else?
Click to expand...

Radar wouldn't be NMEA to the plotter. VHF radio can output DSC position info to the plotter via NMEA.
 
pvb said:
These forums are so confusing, maybe you should go and have a nice cup of tea...
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A UART by the way is a bit of stuff on a processor that converts a byte of data to voltage blips at the correct rate that head off down your NMEA line. You need one per NMEA connection. A UART can either be a hardware module on the processor, or it can be simulated with a bit of software trickery.
 
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