RE: 61 Node CAN Bus

Matt,  

What is the spec of your CAN transceivers on each node? The input
impedance may be causing this.  

Regards
 
Charles E. Pinkstone
Senior Development Engineer
cpinkstone@...
www.liftstore.com
01352 793261
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-----Original Message-----
From: canlist-owner@...
[mailto:canlist-owner@...] On Behalf Of
mddolloff
Sent: 13 May 2008 13:19
To: canlist@...
Subject: [CANLIST] 61 Node CAN Bus


Hey everyone.  I'm new to this board, and to CAN for that matter and
I've got a question.  I've got a CAN bus that we are attempting to
setup.  It has 61 nodes on it (including the VALUECAN USB adapter).  I'm
trying get all the nodes communicating and am having some problems.  Let
me give you the specs.......
Speed: 500kbs
Osc Freq : 40Mhz
Bus length: ~20ft
Wiring: twisted pair
Terminating Resistors: 120 ohms at each end Message Rate: Each node is
sending 1 message/second The symptoms I am having is that as I add in
nodes I reach a point at which all the cards stop sending messages
completely.  I'm not entirely sure why.
Based on all the speed calculations I have done I can't figure out why
the bus is failing.  Could it be  that I need to up the terminating
resistors since I have so many nodes in parallel?  I'm at a total loss
here so any help would be greatly appreciated.
Thanks,
matt
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