Tuesday, May 19, 2009

NMEA FAQ's: What does NMEA have TWO different standards?

Ok, now we're getting to the part of NMEA that can affect your wallet. The best resource for NMEA information -- is directly on the NMEA.org website. Other websites, that promote themselves as experts, tend to get this NMEA 0183 and NMEA 2000 confused. Since the NMEA.org site can get a bit technical, I'm going to de-mystify this for you.

NMEA 0183 (the OLD standard used for marine electronics built PRIOR to 2005)
...is an interface "standard" used to define
  • electrical signal requirements,
  • data transmission protocol and time,
  • and specific sentence formats for a 4800-baud serial data bus.
Each bus may have only one talker but many listeners. This standard is intended to support one-way serial data transmission from a single talker to one or more listeners. This data is in printable ASCII form and may include information such as position, speed, depth, frequency allocation, etc.

NMEA 2000 (the NEW standard used for marine electronics built AFTER 2005)

NMEA 2000® standard contains the requirements of a serial data communications network to inter-connect marine electronic equipment on vessels. The standard describes a low-cost moderate capacity bi-directional, multi-transmitter/multi-receiver instrument network to interconnect marine electronic devices.

It is multi-master and self configuring, and there is no central network controller. Equipment designed to this standard will have the ability to share data, including commands and status with other compatible equipment over a single channel. It is based on CAN (Controller Area Network). All NMEA 2000® products must be certified by NMEA. Although this standard is 50 times faster than NMEA 0183, it is not intended to support high-bandwidth applications such as video.

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