NI-DNET analyzer problem

[illiniengineer]

I'm using a PCMCIA-CAN card, Series 1, first with NI-DNET 1.6.2 and now 1.6.3 and I'm monitoring traffic between an Allen Bradley SLC 5/04 with a 1747-SDN DeviceNet scanner.  The scanner MACID is 62, and the device is MACID 1.  When I start it up, I get normal Dest. MAC and Description fields, as shown here:

If I click the square red "stop" button, and then the green "run" button, I get the following results, with dashes in both MACID fields if the source is 62, and dashes always in the Dest. field.  The description always shows "Unknown".  The PLC and I/O device continue to communicate normally during this time.

To clear this - I unplug the DeviceNet cable from the PLC and plug it in again - this always clears the problem and it starts showing good data again.   Any clues about what is going on?

[Sammy Z]

Hi,

This looks like a bug in the analyzer.  Would you please help me troubleshoot a bit further?

Please save the file after you see the dest. ID and desc. are missing.  Then re-open the dcap file.  Do they still show as - ?

Regards,

Sammy Z.

[frankwu · Accepted solution]

It is an expected behavior in NI-DNET Analyzer.

DeviceNet protocol is a state-machine based protocol. The Analyzer need the connection establishment message to know what a CAN ID is related to a I/O connection.

Figure 1 works well because the Analyzer captures both the connection establishment message and the following I/O or EM messages. So it can parse a packet type and detailed information.

Figure 2 has many "Unknown" because the Analyzer only captures the following I/O or EM messages without the connection establishment message. (Notice: Analyzer doesn't "remember" the last connection establishment message after a new "start capturing". It is to ensures the state machine is monitored in a clean state).

The key to this issue is that always capture the packets including the connection establishment. So the safest way is to start capturing before your DeviceNet scanner starts to work.

NI-DNET Analyzer supports the big file logging. You can log a big file and analyze the messages by filtering or searching.