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Is it possible to use a highspeed (HS) CAN interface for listening to a lowspeed (LS) CAN bus? If so - Is it in any way questionable to do so in a real world car or moped?

As far as I know, LS CAN supports failsafe operation when one signal is broken. I assume, this will not be supported by a HS transceiver.

In my application, I can insure (by means of hard- and firmware measures) that my device is not writing messages to the CAN bus.

So, which risks should I keep in mind when listening on a LS CAN bus?

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  • \$\begingroup\$ I'd make/buy an adapter with two transceivers that converts from one physical bus to the other. Data link layer should be identical, just not the signal levels. \$\endgroup\$
    – Lundin
    Commented Feb 24, 2020 at 14:01

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High-speed CAN (ISO 11898-2) and Low-speed CAN (ISO 11898-3) are different in physical layer.
They are not electrically similar. I do not recommend using a HS transceiver on a LS bus.

High-speed CAN:
enter image description here

Low-speed CAN:
enter image description here

(source)

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  • \$\begingroup\$ Would you see a risk that a HS transceiver interferes with the LS-bus traffic? I only want to sniff, not transmit. \$\endgroup\$
    – Simon
    Commented Feb 26, 2020 at 8:23

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