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Hello
If you are going to connect anything to an existing CAN network, you
can allways kill the communication. This is independant of which
transceiver chip you are using. As long as uou make the right
connections to CAN Hi, CAN Lo and CAN Gnd and the existing bus is
capable to drive one extra device, there is no problem.
The ISO11898-5 standard only describes the "sleeping mode" when there
is no communication on the bus. So you can use your devices in a
low-power mode. It has nothing to do with extra protection.
As long as you are just listening on the bus, you will have no problem
on the J1939 network. Sending messages on the J1939 network is mostly
not appreciated by the truck manufacturers. If you put your CAN
controller in the listen-only mode, you will not be able to send any
message, but if your software is not sending anyway this not really
needed.
The listen-only mode is normally only used as long as you are not sure
that all parameters are correctly. If you have some problem, like
bitrate or CAN Hi and CAN Lo crossed, with your device it will be going
to send error messages on the bus and so have influence on the bus. In
the listen-only mode this will not be the case. However if you see that
you are receiving messages and no errors (your Rx error counter = 0),
there will be no problem to switch to normal mode.
As long as you don't have to connect to the bus used in the connection
between truck and trailer (ISO11992) there is no physical difference
between the busses.
So I advise to use the same hardware for both ports. Possible problems
are mostly created in the software.
Hope this information helps.
Kees Zagers
fflinera schreef op 16.01.2013 18:03:
> My objective is to design a FMS interface device.
> I have planned to use a microcontroller with two CAN modules: one for
> the CAN/J1939 interface with the truck/bus network and the other for
> the CAN/FMS output.
> My doubt is about which transceivers I must use in each part.
>
> For the CAN/FMS output, I suppose that a typical ISO11898-2
> compatible transceiver is OK (a PCA82C251 for example).
>
> But, for the CAN/J1939 interface, I think we need to use something
> special, because I must ensure that my device does not disturb the
> operation of the Truck/bus CAN network in case of failure.
>
> I think that these 2 options are possible:
>
> 1. To use an ISO11898-5 compatible transceiver like TJA1043 from NXP.
> In this case, a bus failure can be detected and the FMS node can be
> disconnected of the internal bus by the microcontroller.
>
> 2. To use an standard ISO11898-2 compatible transceiver (PCA82C251),
> but the Microcontroller CAN module mus be programmed in "listen only"
> mode. in this case, What would happen if the transceiver causes an
> internal vehicle network failure?
>
> Please, Can anyone guide me whether any of these two options is
> correct or is there better solutions?
>
> Thanks in advance.
>
>
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