I made my own version of the Canalyze Linux CAN interface. I plan on using it to study the CAN traffic on a Buick Regal. Since this is a GM vehicle, part of the traffic is on a GMLAN or SW-CAN network.
The Canalyze circuit doesn't directly physically support SW-CAN, so I cut the OBD-II - DB9 cable and plugged the wires straight into the appropriate pins on the car's OBD port, and it worked just fine. I can both send and receive messages, and the MCP2551 does work with GMLAN.
I plan on changing the circuit by adding another two or three MCP2551s so that I can connect to multiple networks simultaneously. Multiple sources indicate that I should use a dedicated SW-CAN transceiver such as the TH8056, but they do not mention why. Thus, my question: are there any disadvantages to using the MCP2551 for interfacing to SW-CAN?
I would prefer not having to mix different chips and I don't see why I would since MCP2551 seems to work with both SW-CAN and high speed CAN.