RE: CAN Request in FMS network

Hi Alberto,

 

The answer is: it depends.  According to the standard the FMS gateway should not pass requests to the internal vehicle network, unless the gateway implements diagnostics support (advertised in the FMS message, SPN 2804, PGN 0xFDD1). In that case, requests for diagnostics messages may be passed into the vehicle network, and results returned to the FMS gateway.

 

FMS gateways may also implement  support for requests (SPN 2805 in same message), which is a bit of a grey area:

-          The gateway should respond to requests for PGNs in the FMS standard

-          The gateway should not forward requests for PGNs outside the FMS standard to the private vehicle network

This can be interpreted in such a way that either the gateway can respond itself to requests for PGNs in the FMS standard, or forward it to the private vehicle network and pass the response. So you don’t really know whether your requests (if they happen to be for an FMS-supported PGN) will be passed or not.

 

So, in theory you cannot really be sure that messages on the FMS network won’t end up in the vehicle network for every type of gateway out there. If the FMS does explicitly tell you that it doesn’t support diagnostics nor requests, it stands to reason that it should be safe. 

 

cheers,

Bram

 

From: [email protected] [mailto:[email protected]] On Behalf Of Alberto Alvarez
Sent: vrijdag 27 maart 2015 17:17
To: [email protected]
Subject: [CANLIST] CAN Request in FMS network

 

Hello,

 

It's been some time since i have been following this list. It is really instructive and I have learned a lot with you.

 

I have a doubt regarding FMS and write operations. I am wondering if it is possible to deploy a private CAN network connected to a OEM FMS. In the private CAN network there will be internal requests but I hope it will not go into the vehicle network.

 

Am i mistaken?

Kind regards

 

Alberto Álvarez