CAN bus connector

Will Reeve · Joined: 30 Oct 2003 Posts: 209 Location: Norfolk, England

I am working on a small board which will have a CAN bus connection. Wondering what people think the best connector to mount on the board? The board has USB, Ethernet (RJ45), RS232 (9pin D) already and the CAN connection is a future option without an application at the moment. Is there a "standard" connection emerging on boards?
I've ordered the CAN dev kit by CCS, does it use a standard connection system?

Benzino · Joined: 15 Feb 2010 Posts: 24

Hi Will,

The CCS CAN dev kit that I have comes with the 3 pin male header for CAN High, CAN Low, and Ground.

In my development, I only use two things for the CAN connection. The official Dsub9 connector or just 2-3 wires solder onto the header or lockable connector. The lockable one should be better since the contact won't loose easily.

Make sure that you have 120 ohm terminate resistor at the each end of the CAN bus if you make your own cable.

Hope that helps a little bit.

-Ben

Will Reeve · Joined: 30 Oct 2003 Posts: 209 Location: Norfolk, England

Hi,
GND....is it needed for CAN communications? It must be a similar situation to RS485? I hate creating GND loops especially on equipment which measures analogue levels. On projects I know are all interconnected inside the same box and hence GND levels between boards / units is the same (or at least within a few volts) I run 2 wires for RS485 even. Is a half way house a 100R resistor connecting CAN GND to board GND, at least it will act as a fuse!

collink · Joined: 08 Jan 2010 Posts: 137 Location: Michigan

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Will Reeve · Joined: 30 Oct 2003 Posts: 209 Location: Norfolk, England

Very interesting reading chaps. Thanks. I am apprehensive as I've had no end of trouble with GND in USB connection, so much so I always optically isolate a USB interface with a PIC now.

I also use a RS485 GND isolated transceiver if the board can absorb the cost (and external RS485 is needed). Looks like CAN is much more robust. I am going to use a MCP2551 which has a "automatic thermal shut-down" which reads like it will protect itself if a GND potential difference causes a large differential span (and hence current flow). I am going to put a 3 pin header for CAN, include GND and make a note in the handbook accordingly.