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Thoughts on our NMEA devices and software, NMEA0183 and NMEA2000 protocols, and related matters.


Gateway, Converter, Bridge, Router or Adaptor?

Manufacturers have different names for their gadget that converts between NMEA and Wi-Fi - gateway, switch, converter, adaptor or plain device. I thought it would be interesting to look at what these different terms mean, and so decide what is the most appropriate nomenclature.

Gateway and Protocol Converter

A gateway is a node on a network that interfaces two networks using two protocols, converting between them so data can flow between the two different protocols. For example, converting between any of NMEA0183, NMEA2000 and TCP/IP. A protocol converter is basically an alternative name for a gateway - netwok engineers tend to talk about gateways, whereas electronics engineers talk more of protocol converters.

Hub, Bridge, Switch and Router

All of these devices connect two or more networks together, but don't do any protocol conversion. 

The router keeps the networks separate, just passing data between them. So it can be applied to your broadband router, which connects the external broadband and internal wired and possibly Wi-Fi networks, as these all run over TCP/IP, but it won't convert from TCP/IP to another network protocol, and it doesn't make a single seamless network.

The hub, bridge and switch all join the networks together seamlessly. Examples are connecting together CAT5 and Wi-Fi networks, or connecting two segments in a large NMEA2000 network. The simplest is a hub, which just retransmits all incoming data on all output ports. Bridges generally just connect teo networks, and can have some intelligence in deciding what data is sent between the networks. Switches are the most advanced, with a lot of built-in intelligence, so minimising the load between the networks.

Adapter (or Adaptor)

This is a generic term that can refer to many things, but basically it is connecting two different devices. It may be as simple as the 9 to 25 pin adaptors of RS232 networks, where there is no electrical conversion. Or it may also convert the signal, like an RS232 to RS485 adaptor. In a computer, the network adaptor is the interface between the computer and the external network, whether a chip on the motherboard, an add-in card or a USB device. So this is a catch-all term that can cover virtually anything.

And as for adaptor versus adapter, either are fine for the device, with the English preferring adaptor and the Americans preferring adapter. But a person adapting something is always an adapter.

So What's the Right Answer?

A device going between NMEA0183 and Wi-Fi is a gateway or (protocol) cConverter, as it is going from the NMEA0183 protocol to TCP/IP. Whilst some manufacturers call it a router, this isn't correct, as it is converting the data between two protocols. Some manufacturers sidestep the problems of nomenclature by just calling it a an adaptor, but to my mind this is too generic a term to be useful.

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