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I am using a Freematics One+ B for my project and to avoid developing and testing in a car, i would like to simulate ODB messages. I already have a Vector CAN emulator (VN1610) which creates proper CAN messages.

The problem i am facing is, the CAN emulator i have just provides a GND,CAN_ HIGH and CAN_LOW. On the other hand, the ODB scanner (Freematics One+ B) has more pins that connect with the actual Car ODB port, namely:

  • 4,5 : signal ground and chassis ground (i will hook them together for now)

  • 6,14 : CAN_H, CAN_L (goes to corresponding can pins)

  • 7,15, ... : Other vendor specific pins such as IS0 9141 (not related)
  • 16 : Battery Voltage 12V

My question is, do i also need to hook up an external 12V battery to Pin 16 for this to work, or is there something i am missing and its not even possible to do this.

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  • \$\begingroup\$ Yes, you will have to hook it up, the +12V is the supply for the Freematics. \$\endgroup\$
    – Ron Beyer
    Feb 20, 2020 at 15:23

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CAN bus part of the Freematics board is powered through the 12V pin of the OBD connector. The signal is manipulated with a series of cascaded step down converters to fit the power needs of the rest of the circuit. You can follow it from the schematic.

In short yes you need to connect the 12V pin.

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