I have an application where there is an existing Profibus network that I need to tap into. I need to use a Compact RIO. Basically I just need to read the data on about 12 specific tags and generate some outputs on cRIO. The question is, can I just listen to whats going on on the PB network without being a slave or a master on the network? I have the PB master/slave module for cRIO. I need access to the data with minimum interruption of the network that is already in place. Is this possible, and if so, how would I go about doing it? Thanks for the help!
You can ether get a network analyzer or use a serial card, such as a 9870, to listen to the raw bytes on the line. Depending on how much communication you need to analyze the network analyzer will pay for itself pretty quickly.
Thanks for the reply. What I need to do is listen to a only a couple of specific devices and repeat their data as analog outputs. The signal manipulation stuff is easy - but what I hope to be able to do is listen to messages that are sent from particular devices, without having to include the cRIO as another device in the network. I just want it to be a fly on the wall so to speak. Is that possible with the PB modules?
It won't be easy, we have a chip on the module that processes communications. You will never see the data meant for other slaves because it will be filtered out right at the bus. This is something you won't have control over. Your situation sounds like something that a network analyzer should be used for though, unless you are in special circumstances I would look towards that.
From a technical standpoint what you want could be accomplished with a 9870/71 with some extensive FPGA programming or by programming the profibus master to repeat communications to the cRIO.