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Thread: Switching of signal lines

  1. #1
    Junior Member
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    Aug 2019
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    Switching of signal lines

    I'm working on a CAN bus sniffer/splitter/injector based around the Teensy 3.6 (might move to the Teensy 4.0 for final device). As it stands it's working fine in prototype form, and I'm ready to build a board and make it a useable item. It sits between two nodes and my philosophy is that to be a true sniffer there should still be a direct connection between the nodes, (rather than traffic routed through the device as it does in my prototype), with the sniffer just connecting to the bus as an additional node. To use it as a splitter though this connection must be broken, which I could do with a physical switch or a couple of transistors controlled by the Teensy. The transistor solution on the CAN H and CAN L lines would be my preferred method, but I'm unsure as to how this might effect the signal quality. This is all for a specific bus that runs at 500Kbps. I suppose a third option would be a miniature relay which I do happen to have on hand.

    What do you guys reckon would be the best approach? Building a circuit is something I can do reasonably well. Choosing the right components for the right reasons is not something I'm good at. It's all just guesswork for me.

  2. #2
    Junior Member
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    Anyone got any suggestions? I'm favoring the relay approach right now, because I just don't know enough about transistors.

  3. #3
    Senior Member vjmuzik's Avatar
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    Apr 2017
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    Since you have a relay on hand already I say test with that and see how it performs, it should perform well since itís a direct connection through a relay and not flowing through a transistor, it takes out some of the guess work.

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