Quote:
Originally Posted by Al Skierkiewicz
Also, the CAN buss should never be parallel wired. In short systems it may seem to work but, as is typical, this system will fail you when you need it the most.
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Hate to disagree with you, Al, but CAN as a standard is supposed to be a multidrop communications protocol - it's specifically designed to be wired in parallel. In fact, most CAN devices don't have termination built in; they expect termination to be included at either end of the bus. Now for the caveat: I believe the variation of CAN FIRST uses is called Falut-Tolerant CAN, which has terminations at every endpoint, and expects the daisy - chained connection topology implied by the in/out ports of the speed controllers. This means there is a termination at every endpoint, which, when wired in parallel, drastically reduces the overall bus resistance and causes the voltage swing to drop (CAN, like most differential signalling schemes, is current driven instead of voltage level driven). So, while I agree FIRST teams should definitely not connect their devices in parallel, CAN in pretty much any other application is designed to be used as such. Just so none of our bright young minds gets the wrong idea about CAN.
-Sparks
Edit: The Talon SRX manual recommends a parallel linear wiring topology. They're not doing any crazy - just vanilla CAN. Absolutely wire your CAN in parallel