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I would like to read CAN signals from my car over the OBD-II connector.

My question is, whether I need to implement any kind of (overvoltage) protection, so the Adafruit won't get harmed (and vica versa), or I can connect the CAN signal lines directly to the Adafruit?

Thank you very much for your answers in advance!

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  • \$\begingroup\$ How do you intend to supply your external board? USB? \$\endgroup\$ Commented May 21, 2024 at 11:34
  • \$\begingroup\$ I can take it from the OBD-II connector itself, though I would need a DC-DC converter circuit. Another convenient way would be just powering it from my laptop or a power bank via USB, though I'm a bit worried that some current can be back-fed into the car.... \$\endgroup\$ Commented May 21, 2024 at 12:21
  • \$\begingroup\$ In that case maybe add reverse polarity protection and definitely TVS on the supply. \$\endgroup\$ Commented May 21, 2024 at 12:34
  • \$\begingroup\$ Solder a TVS into the USB cable? Don't want to incorporate +1 PCB. Sorry, I'm rather a SW than a HW engineer. \$\endgroup\$ Commented May 21, 2024 at 12:48
  • \$\begingroup\$ That was under the assumption that you'd take supply from the OBD connector. Either way it's not nice to "hot plug" powered boards together and the OBD connectors don't seem designed to be used in that way(?). As in ensuring GND pins touch first. \$\endgroup\$ Commented May 21, 2024 at 12:51

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The MCU board has a CAN physical interface. It should be generally safe to connect to another device with a CAN bus, if done properly.

The TCAN1051HGV is a fault-protected CAN transceiver. However as the exact part number in the BOM is not known, it's likely not the automotive grade version of the chip.

Now, if you fry up the MCU board, it's cheap enough you can always buy a new one. The same unfortunately may not apply to your car.

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  • \$\begingroup\$ Thank you! So I can fry the car with this Adafruit board? \$\endgroup\$ Commented May 20, 2024 at 21:31
  • \$\begingroup\$ @Zsolt Unless you do ridiculously clumsy things like shorting CAN GND with 12V etc there's no reason to believe you will be harming anything. \$\endgroup\$ Commented May 21, 2024 at 11:04

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