Can Bus

"terry" wrote

Most people do (I == 'most people').

-- Nicholas O. Lindan, Cleveland, Ohio Consulting Engineer: Electronics; Informatics; Photonics. Remove spaces etc. to reply: n o lindan at net com dot com psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

"Nicholas O. Lindan" wrote

Or did you mean the physical & link layers (drivers and controller ('uart'))?

"Most" people use the CAN controller embedded into some microcontrollers, or a standalone CAN controller (e.g. Intel 82527), or a licensed CAN core into a FPGA. I think it's illegal to implement a software version of CAN protocol for commercial purposes without buying a license from Bosch.

software?

Oh, that kind of illegal.

Agreed. I responded with a knee jerk: as in RS232 meaning asynch serial when it really means voltage levels and modem protocols.

CAN, formally, is the hardware spec.

When I worked on the software that used CAN it was called the 'CAN software' -- i.e., CAN is implemented in software

-- which isn't true. There are high level CAN protocols (CANopen, AB's DeviceNet(?)) in the public domain, of a sort.

The CAN part of CAN is, well, canned.

That said, for slow baud rates I would think you could implement the CAN controller part of CAN in microcontroller software in the same way a UART can be implemented in software.

As to the legality of using the ISO specification for CAN, to the best of my knowledge anyone can build to the standard, as in RS232. Some standards, IrDA(?) and HP-IB were (are?) proprietary, though.

I don't know of any proprietary successful standards.

Maybe this is the point (see below).

I agree. If you look at the open source CAN core at opencores.net, you'll see that it is not so complicated after all.

I think that you are right when you say that formally the "CAN standard" defines just the physical level. But I think that the rest (data/transport layer, CDMA and algorythms in general) is patented to Bosch. This is very much the same of saying that the entire CAN protocol is proprietary. ;)