CAN Nodes and Termination question!!!

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
I have a question concerning the line impedance of Can bus.
Currently we are communicating from an ECM to a Cluster with CA
protocol.
Each ECM and Cluster has a 120 ohms resistance inside for the impedanc
termination.
We are communicating at 250 kbauds on a really short distance, like 1 or
meters.

Sometimes we branch a laptop on the bus to make a diagnostic.

The question is: When nothing is branched in the diagnostic plug, do w
have to branch a 120 ohms resistance or we can lets it free.

Second question: Does the nodes for the diagnostic plug have to be exactl
at the same distance on the bus, or one (CAN_H) can be closer of the EC
and CAN_L closer of the cluster




Re: CAN Nodes and Termination question!!!


Quoted text here. Click to load it

There is no such thing. CAN is commonly used through a pair of wires with
unspecified line impedance.

Quoted text here. Click to load it

This is not right. There should be just two terminators at the farthest
points of the bus.

Quoted text here. Click to load it

You should not worry about anything at this kind of distance.

Quoted text here. Click to load it

Leave it open.

Quoted text here. Click to load it

It doesn't matter at 1..2m cable length.

Vladimir Vassilevsky
DSP and Mixed Signal Consultant
www.abvolt.com







Re: CAN Nodes and Termination question!!!
On Sep 24, 9:22 am, "Vladimir Vassilevsky"
Quoted text here. Click to load it

My understanding was that CAN was to be run through twisted pair cable
with a 120 ohm characteristic impedance. A quick google found this
primer by TI that mentions the same on page 16:
http://focus.ti.com/lit/an/sloa101/sloa101.pdf.

Of course, for his app, I can't imagine it'll matter in the slightest.

-Michael


Site Timeline