CAN Bus Man-in-the-middle monitor for reverse engineering. Based on the TI Isolated CAN FD Repeater Reference Design (https://www.ti.com/tool/TIDA-01487) this circuit board is designed to be placed between a CAN Bus and a specific ECU to identify CAN Bus messages originating from that ECU. It is a CAN Bus repeater with two additional CAN Bus ports to send the bus traffic to an external logging device. It can also be used as a simple repeater to allow communication with an existing bus without adding a large stub for the external device (allowing it to be remote from the system under study).

It supports both classic CAN and 2 Mbps CAN FD (untested in my design, but claimed by TI for their circuitry). It is designed to be powered by a vehicle 12V power supply (7-16 VDC input) with a common ground between CAN devices and the CAN monitoring system. The power input is reverse-polarity protected.

The CAN1 and CAN2 ports have an optional 120-ohm termination resistor. The CAN1 MON and CAN2 MON ports have a built-in 120-ohm termination resistor.

A simple OpenSCAD 3D printed enclosure is included here and the and associated STL files may be found in my repo (https://github.com/danjulio/can_mim_mon). Be sure to slice with supports.