I would like to build a packet analyser that performs one or two of the tasks of Bus Monitor. Need information on function calls.

[wishfulThinker]

I have gone through the communication manager documentation and have basically found out how to:
- open a session ( nifOpenSession )
- check for interfaces ( nifGetInterfaceList )
- open a link ( nifOpenLink )

The rest of the documentation talks about how to modify parameters.

I am looking for something to just read the data stream on that link. This would be similar to how I think Bus Monitor does it. I do NOT need any information on how to decode the data. I will get that from the fieldbus standard. I just need to know how to capture that raw data stream.

Any help would be appreciated.

[Fbus]

Sorry that there is no API interface like NI-FBUS Communications Manager API for Bus Monitor.

And as I know, NI has no such product having API interface to acquire raw data stream like Bus Monitor.

[wishfulThinker]

Really?

OK...how about any other way to capture the raw data stream (Other than API calls). The NI card does interpret the Manchester encoding so the data is there.

Looking at the API calls, it does allocate a buffer for all reads. But I guess they are only used for those specific functions. There has got to be a way to pry open these API calls and figure out how to get the raw data stream.


Any insight would be appreciated.

[Fbus]

You are right, NI-FBUS CM API only allocates buffer for Read/Write operations(nifReadObject and nifWriteObject).

If you want to decode the raw data stream, you might use NI Fieldbus Communications Stack to get the raw data; but the stack is working as a device(Link Master or Basic Device), and it can't capture data stream among other devices. By calling the stack, you can capture the raw data based on SM_READ/SM_WRITE service, but you can't capture all the other packets like Token Passing, SET_TAG, IDENTITY, SET_ADDRESS or NM related packets.