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Is PROFIBUS communication possible with a simple RS-485 output?

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I may need to communicate to a PROFIBUS DP equipped device and am looking at my options. There is a profibus module NI sells but at $1500 each I'd like to see what else I can do... I need only about 9600 baud to one slave so standard serial port performance is adequate. So from what I understand profibus physical layer is basically RS-485 2 wire. So would it be possible to communicate with a profibus device using my cRIO 9035's built-in rs-485 output? Seems like it should be doable.

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Accepted by topic author MarkCG

Hi Mark,

 

While it may be technically possible to do PROFIBUS communication through the cRIO's built-in serial port, I don't think it would be supported by NI's PROFIBUS driver, meaning you'd essentially have to code the driver yourself to get it to work. If you're OK with that you can certainly give it a shot, though I'm not sure the extent to which this would be supported by NI.

 

Additionally, and perhaps more importantly, in using the serial port I believe you'd lose the PROFIBUS benefit of deterministic communication, since standard serial communication is inherently nondeterministic. With the module, determinism would be ensured.

 

Nick

Applications Engineer

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Ah thank you for your reply. Well determinism isn't important in this case but yes I definitely am not going to code the PROFIBUS protocol from scratch. I guess I'm either going to get the cRIO profibus module or a modbus-profibus gateway device. The profibus cRIO module forces you to keep one slot empty next to it so I am prob going with the gateway.

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