Quote:
Originally Posted by Dale
An active star module that allowed every jaguar to remain at it's default address of 0 would be very cool.
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That would kind of defeat the advantages of CAN networking though (the added complexity of the "router")
But there is no reason CAN can't be used in a star topology. We use a star topology in the cars where I work, on both the 125 kb/s and 500 kb/s networks. The key is proper terminations.
Terminating resistors are intended to prevent the signal reflections that occur at the end of an open-circuited wire. What happens is the signal hits the open wire end (at the speed of light) and bounces back into the network (at full amplitude). Do this just wrong and your data bits turn into garbage.
A good tool to see if your star network is well-terminated is an oscilloscope. Compare a known-good signal to your network.
Regarding noise: A CAN-Bus is inherently resistant to noise, since it uses differential signaling. It is the difference between CAN-H and CAN-L that determines logic 0 or 1. In theory, both wires of the network will be affected equally by some induced noise, while the difference between the wires remains constant. In practice, the noise induced into each wire is "same" enough to work against noise very well.