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Using EtherCAT for realtime data gathering on TurboPMAC


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Since the upload bandwidth of PMAC gathering data is limited using the standard communication interface with "RHL" memory commands, we want to extend an existing machine based on a TurboPMAC Brick Controller with an EtherCAT interface by using the 'EtherCAT Slave' fieldbus option (ACC72EX based solution). The product handling part of the machine (a standard PLC based environment) already has EtherCAT as the main I/O fieldbus.


The idea is to make the Brick an EtherCAT slave and to publish the required gathering items 'realtime' on the EtherCAT bus using PLCC0 and the DPRAM interface of the ACC72EX module. The standard EtherCAT scope tools (by Beckhoff) could then be used for the data gathering and visualization.


Is this a feasible use-case of the EtherCAT option on the Brick controller?

And if so, would the bandwidth be enough for a 1 kHz update rate for about 10 gather items?




Jan van der Meer

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How are you using the "RHL" command to acquire the gathered data?


Note that the "list gat" command would use the full bandwidth of PMAC communications.


You should be able to accomplish a 1KHz update on the DPRAM with a PLCC0.


Thanks for your reply.


Off topic:

I don't think 'LIST GATHER' upload of gathered data is more efficient, since basically it gives the same data as 'RHL' commands that uploads blocks of data. We developed our own version of PmacPlot with a more advanced gather data handling, like 'realtime' data upload while gathering, support for cyclic gather-buffer handling and of uploading of 'old' gather data while a new gathering has already started (but did not overwrite the unread data yet). The standard PmacPlot32Pro2 does not support this and can't handle configurations with multiple simultanuous TCP/IP connections the PMAC without blocking other sockets (or at least some years ago could not).


On topic:

Use the of ASCII-based data upload though the standard command interface requires too much bandwidth for our new data gathering requirements, at the moment we don't have the DPRAM option on our Ethernet Brick. In addition gathering data must be 'pulled' from the PMAC instead of a streaming way initiated by the PMAC, and therefore we want to use EtherCAT-slave option to publish the data realtime (the EtherCAT bandwidth itself should be sufficient for that).


Are you aware of any (standard PMAC, non PowerPMAC) applications that use a similar approach like this?


At this moment I don't have enough experience with EtherCAT and the Hilscher ComX Module option for the BrickController (that we didn't order yet) to overlook all possible limitations and pitfalls, and how much effort is needed to get it working with the Beckhoff scope tools.

Therefore I'm searching for feedback if this EtherCAT solution is useful way for high-speed 'realtime' data gathering, and I hope DT people or other forum users can guide us with that before we order and setup a prototype environment.



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Off topic:

The 'LIST GATHER' will provide all the data at one time without the line-by-line overhead of 'RHL' commands.


On topic:

I don't know of anyone doing this method but I think it would be relatively straightforward. I don't know enough about the Beckhoff scope tools to answer this completely. I would think using PMAC data gathering with an appropriate Windows application might be a better solution.

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