rusefi.com

This is a neat and interesting device. It sniffs CAN bus with out breaking the wires.

http://www.gps4net.com/can-obd2-interfaces/g4n02tap-wire-tapping-contactless-reader-can-bus-jbus-fms-j1939-j1708-j1850-j1587-iso11992-iso11783-obd2-telematics-standard.html

That's pretty amazing. I'd be interesting in trying to build one.

They post a back side picture, doesn't look very complicated.

kb1gtt wrote: ↑

Sun Sep 13, 2020 1:06 pm

They post a back side picture, doesn't look very complicated.

That SOIC8 on the top is a normal CAN transceiver, SN65HVD1050. The SOIC14 below it is an MCP6564 quad comparator.

So whatever they're doing is clever, but not terribly complicated.

My guess is the comparator is used in Schmitt trigger fashion to amplify the induced voltages from the coils (air-core transformer) laid into the board. That signal is then fed to the CAN transceiver to drive the CAN output. Differential signal in, easy to amplify. As the site said, RS-485 is compatible as well, which is also a differential signalling system.

Similar but different. It's an ESP32 wireless can bus gateway.