ELM329LP datasheet(55/87 Pages) ELM

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ELM329L DSA

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ELM329L

Several European heavy duty truck and bus

manufacturers have joined to form an organization for

standardizing the way in which information is retrieved

from these large vehicles. The result of their work is

the FMS (or Fleet Management Systems) Standard,

and the Bus-FMS Standard.

The FMS standard is based on a subset of the

250 kbps J1939 protocol, which uses only broadcast

messages

for

the

information.

order

not

compromise the integrity of the vehicle’s CAN bus, the

standard also specifies a gateway device to provide

separation between (potentially unskilled) users and

the critical control information on the vehicle.

The information contained in the FMS messages

is defined by PGNs, using the same PGN numbers as

for J1939. The difference is that they only define a

small subset of those specified by J1939.

To monitor the information provided by an FMS

gateway, simply use the AT MP command with the

The FMS Standard

We are occasionally asked about support for the

NMEA 2000 marine standard. Elm Electronics does

not provide specific support for this protocol, but our

ELM329 integrated circuit is very capable of working

with the protocol.

While the physical connectors may look quite a bit

different than those used for J1939, the CAN interface

and the data format is almost identical to that of the

J1939 standard. NMEA 2000 uses a 250 kbps data

rate, so the easiest way to get started is to select the

ELM329’s predefined protocol A. This is done with the

set protocol to A command:

>AT SP A

When you are finished and want to use the

ELM329 for standard OBDII protocols, don’t forget to

send the AT SP 0 command to reset it.

Many of the PGNs used for NMEA 2000 have

values that are greater than 65535, so the DP bit is

usually set. To monitor for most PGNs then, you can

not use the short version of the MP command. For

example, to monitor for the Engine Parameters PGN

(127488 or hex 1F200), you can not use:

>AT MP 1F200

as the ELM329 actually interprets that as a request for

The NMEA 2000 Standard

appropriate PGN number. We should caution that

some information (VIN, software version, etc.) is only

transmitted every 10 seconds, so some patience is

required when waiting for the data.

The FMS standard is completely open, and still

evolving (as of this writing, the latest update was

version 2.00, dated November 11, 2010). For more

information, visit the web sites:

FMS Standard

http://www.fms-standard.com

Bus FMS Standard

http://bus-fms-standard.com

PGN 1F20, and get 0 replies. To monitor for PGN

1F200, you must send:

>AT MP 01F200

If you keep the above in mind, the ELM329 will

prove to be a handy tool to use while experimenting

with NMEA 2000. It does have a couple of limitations

that must be kept in mind, though. As mentioned with

J1939, it is not capable of address negotiation. Also,

the ELM329 does not currently support the Fast

Packet protocol, which may be an issue for some

users.

For more information on the NMEA 2000 standard,

visit the NMEA web site:

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