CAN BUS protocol stack

Question

Can someone explain to me what is CAN BUS protocol stack? Is it CAN BUS+ higher layers, like CANopen with 7 layers or something else, and can someone explain how can I use CAN stack, how I connect it with CAN bus, and why I need it?

Thank you

Answer 1

Yes it is CAN hardware with higher layer protocols, such as CANopen, J1939 or DeviceNet.

In terms of the "OSI model", it only really makes sense to speak of layers 1-3 and 7, where CAN is layers 1 and 2 and a protocol like CANopen roughly provides layers 3 and 7. Roughly, since CAN-open also comes with hardware specifications such as baudrate, sync point & stub length recommendations.

What's known as a "protocol stack" is really just a library with a platform-independent API, usually delivered with hardware-specific drivers. If the vendor claims that they support a particular MCU, then it usually means that you get the drivers from the vendor.

So basically you buy this pre-made library and integrate your program with it, then get standardized protocol behavior on the CAN bus, necessary to communicate with other nodes implementing the same protocol. Writing such a library yourself is no small task, particularly not for CANopen which is a big standard, where you are probably just going to use some 10% of the available functionality.