One thing I wanted to ask ... why yet another electrical standard .. we have loads of multi-drop systems from RS422, 485, I2C, CAN, ethernet (multiple protocols), as well as the drive-by-wire systems used in cars. Why do we need NMEA specifically for boats? -- Shane
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Shane, The NMEA 2000 Standard is based CANbus and the cable specs that are part of it are based on the DeviceNet standard that's often used with CAN.
The main thing NMEA added was a growing set of boat specific data formats. NMEA 0183 is also mainly about putting boat specific data into a standardized format (without CAN's true networking, automatic addressing, data prioritizing, etc.). How else could a sensor send out, say, Speed Through Water and have it understood by all sorts of boat electronics?
Really it's too bad that there's not a NMEA standard based on Ethernet (yet?). The way it works now is that you can connect almost any manufacturer's radar scanner to almost any manufacturer's multi-function display via an Ethernet hub, but you'll get nothing but trouble unless they are the same manfacturer's, often even the same model series.
Do you know where I can find the packet specs .. I guess they are being added to fairly frequently as new devices are developed. I want to build a full engine monitoring system(12 EGT, 3 water, 4 oil, fuel flow, for each of 2 engines) but would prefer if it was based on industrial ADC's, and use "drivers"('doze, or preferably Linux) rather than construct a new format.
NMEA survives on members dues and by selling the output of its committees. If they did not survive, we would be back to a teetering tower of babel as each inventor/ developer/ manufacturer chose whatever he liked as a label for each type of data that moved between devices. Imagine a country where different telephones had different key pads and everyone got to decide what their telephone number is regardless of what someone else chose. That was what we had before NMEA.
You aren't, by any chance, considering yet another different tongue for the teetering tower are you??!? It would be more useful to develop a translator, (such as already exists for a couple boat units)
I think I read somewhere that NMEA is working on a second generation version of NMEA-2000 based at least in part on Ethernet.
True? If so, any sense of when it might be offered? And, what will be the impact on existing NMEA-2000 devices and cabling?
I don't think so, RO. I do believe that NMEA is working on a marine Ethernet standard, but the intent is not to replace NMEA 2000. The two can co-exist on a boat very well, already do on many. Heck, there are still sensible uses for NMEA 0183, and NMEA just put out Version 4.0.