Re: CAN Request in FMS network

Hi Bram


Thank you very much for your elaborated response. This* "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*" was exactly what I
was afraid of.

I must seek for a better way of integrating a read-only version of FMS data
with my system.

Kind regards & congats on the outstanding support you provide

Alberto Álvarez

On Mon, Mar 30, 2015 at 10:01 AM, Bram Kerkhof <[email protected]> wrote:

> 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
>