Cable & Connectors for CAN bus

[Eric Anderson]

Is there a standard for CAN bus cable? Are there limitations as to the
cable and connectors to be used? I know that Vector Cantech uses DB9
connectors. I know of someone that is contemplating to use RJ11
connectors and the cable typical cable used for those connectors. It
would appear that the cable should have a characteristic impedance of
somewhere around 120 ohms since that is the termination resistor that
appears to be recommeded.

Can anyone direct me to further information on the subject or tell me
their experiences or thoughts?

 

[Tim Wescott]

Is there a standard for CAN bus cable? Are there limitations as to the
cable and connectors to be used? I know that Vector Cantech uses DB9
connectors. I know of someone that is contemplating to use RJ11
connectors and the cable typical cable used for those connectors. It
would appear that the cable should have a characteristic impedance of
somewhere around 120 ohms since that is the termination resistor that
appears to be recommeded.

Can anyone direct me to further information on the subject or tell me
their experiences or thoughts?

The CAN standard, by itself, doesn't specify the physical medium to be
used. Anything that can be made to be passive 0, whether it be a
twisted pair, a line on a board with open drain drivers, foghorns, or
the level of beer in a trough, can all be used as physical media with
suitable transceivers.

The limitations are the aforementioned passive 0 property, and a baud
rate limitation that's determined by the speed of information
propagation in the chosen medium and the length (beer in a trough
performs much more poorly here than twisted pair).

There is an SAE standard for one particular CAN bus that specifies the
electrical bus. It's the one most often designed to by 'CAN
transceivers'; it calls out a twisted pair with resistive termination, a
'1' is no differential voltage and a '0' happens when one or more
transceiver is driving the pair.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

 

[dalai lamah]

Un bel giorno Eric Anderson digitò:

Is there a standard for CAN bus cable?

Yes, 120 ohm balanced twisted cables, see ISO 11898.

Can anyone direct me to further information on the subject or tell me
their experiences or thoughts?

My experience is that in most cases automotive wirings don't use expensive
cables; any twisted cable is just fine, even at 1 Mbps. Probably the
expensive cable is necessary when you go near to the limits of CAN bus
specifications; the common automotive wirings are far less critical.