USB Profibus PC-Adapter


Thread Starter



I need a Profibus adapter, which will be used in the field. Because of that is must have USB. The host system is SIMATIC PDM. So PDM must handle this adapter. Nice would be if Pactware and Co. can also handle with this adapter.

I hope someone can suggest the right adapter.

Thank you in advance.
What are you planning to do with the PROFIBUS interface in the field? Are you going to connect it to a running PROFIBUS network? I'm not sure you can... I personally believe PROFIBUS was not really made to have "temporary masters" connected, like a handheld field communicator or a laptop. PROFIBUS originates from the PLC world where they don't do daily calibration and commissioning the way we do for instrumentation in process control.

Profibus support multiple class 2 masters (which are used for calibration
and diagnostics) but the challenge is the bus parameter need to be the same as for the other masters. I personally believe the chances of getting the master class 2 configuration wrong, risking upsetting the bus, is high. It may be impractical to change these settings in a laptop as you move from one bus to another. You may wish to double check this with a PROFIBUS expert.

This is why there is no handheld for Profibus (only for FF and HART) and why Beamex says their documenting calibrator must be connected offline for Profibus (but can be connected to running bus for FF).

FF meets NAMUR NE 74 clause 3.1 and 5.1. It may be a better option for you if we are talking about instruments like transmitters and valves.

To learn more about fieldbus and Ethernet and stuff you did not know about HART take a look at the yellow book "Fieldbuses for Process Control: Engineering, Operation, and Maintenance" buy online:


James Powell

Both Siemens and Softing make a USB to PROFIBUS DP adaptor that work with SIMATIC PDM. The Siemens one is called CP5711.

I am a certified PROFIBUS network engineer and I can assure you that the previous comment about PROFIBUS was not correct. PROFIBUS was designed to allow multiple master (both controllers and engineering stations aka class 1 and class 2 masters). Taking a programmer and connecting and then disconnecting from the bus is not a problem.

Here's why I personally think temporarily connecting a portable master on a running Profibus is a challenge. It can be done, but is not plug-n-play.

All masters on the Profibus must have the same bus configuration. This means same baud rate, same target rotation time, same slot time, etc. This is easy for permanently connected masters. It is a little trickier for portable masters connected ad-hoc each time to a different network as and when required.

So if you are in the field and walk up to one of your DP networks with a laptop and interface, you need to configure the interface according to the network you intend to connect to. That is, you must first check on the system engineering workstation: the baud rate, target rotation time, slot time, etc. and set them identical in the laptop interface before connecting to the bus. Each bus in the plant has different settings because they have different devices, and maybe different PLC and communication card, etc. Also make sure to configure an address for the interface card not used by other node on the bus. It may be a good idea to connect the interface to the bus before starting the software.

I personally find FOUNDATION fieldbus (FF) and HART easier because:
- For HART there is no master address to set (primary and secondary master are distinguished by timing), so you cannot set it wrong, so you will not crash the communication. The baud rate is fixed, so you cannot set it wrong, so you will not crash the communication. There is no timing settings...
- For FF there is a standardized address range for temporary masters and addresses are assigned automatically by the system, so you cannot set it wrong, so you will not crash the communication. The baud rate is fixed, so you cannot set it wrong, so you will not crash the communication...

Another good thing about HART and FF is that the laptop interfaces connect directly to the device or bus cable to the device so field work is possible (and yes all field instruments need to be worked on in the field at some time: field.pdf).
There are also FF and HART handheld field communicators available that are easier to carry around than a laptop and interface. And these are intrinsically safe too.