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When connecting a CAN bus, does the polarity of the two lines matter, or is it simply the differential that the circuit decodes?

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Yes it matters, CAN_H of either device has to connect with CAN_H of each other and same for CAN_L as well as shown below.

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  • \$\begingroup\$ It might be worth adding that the effect of not doing that is that every data bit that is sent gets inverted. \$\endgroup\$ – Tom Carpenter Aug 15 '15 at 21:42
  • \$\begingroup\$ Actually, bits aren't inverted with can, the bus won't work at all. With CAN state 1 is "recessive" and differential voltage is close to zero. State 0 is "dominant" and there CAN_L goes low and CAN_H goes high. \$\endgroup\$ – TemeV Dec 12 '18 at 21:25
  • \$\begingroup\$ Oh, this was an old question that popped up to front page... Well I'll still leave my comment there :) \$\endgroup\$ – TemeV Dec 12 '18 at 21:26

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