SDO accesses interfere PDO update loop? about pysoem HOT 9 OPEN

I can't really tell. For now I can't even think on how to do this nateivly with the SOEM API itself. Maybe you could find something about this in the SOEM issue list.

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Thank you for your reply.

To solve the problem fundamentally, I would like to add a process in my program that performs a PDO update cycle.

I referred to this issue: OpenEtherCATsociety/SOEM/issues/405.
According to this discussion, SOEM is designed to be thread-safe except for PDO.
Therefore, I think this issue can be resolved by adding a process for the PDO update cycle.
Locking other functions will prevent the PDO update cycle from being interrupted.
However, I find it difficult to implement the PDO update cycle process myself.
This is because pysoem.Master is not picklable and cannot be shared by functions in python's multiprocessing module.
Therefore, I think the process of PDO update cycle should be implemented inside pysoem.

If that is not possible, simply making the timeout arguments for sdo_read and sdo_write adjustable may alleviate this problem.
It is currently given an immutable value, EC_TIMEOUTRXM = 700,000 us = 700 ms, which is too long to run at the same time as the PDO update cycle.

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Putting PDO update cycle in a process inside pysoem, sounds good to me. But to figure out how to implement this, I need to take a closer look at things. You still need a way to update the PDO data, synchronized with the PDO process.
Making the SDO timeouts adjustable is much more a short term issue, and is already on my todo list. Here I think of a Master.sdo_timeout property that is applied to the SOEM SDO read and write. But maybe this only possible on a per device basis.

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Hi @tanakarei256 ,
I have same problem right now.
I read your comments and this issue OpenEtherCATsociety/SOEM/issues/405
And mostly understand problem but ı dont know how to do it really. Can i solve problem with pysoem ? And can you explain me little bit more ?
Thank you.

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I'm not familiar with SOEM or EtherCAT, so I don't know how to implement it.
For my purposes, I think it's enough to have a function that waits for the next PDO update for synchronization.
However, more features may be needed for other uses.

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Hi @tanakarei256,
at least the SDO timeouts are now configurable. Check out pysoem.Master.sdo_read_timeout and pysoem.Master.sdo_write_timeout. This will be availabel in the latest version of pysoem (1.0.2) installed via pip from PyPI.

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Thanks for the improvement.
I think that shortening the timeout for SDO communication has reduced the problem.

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Can I control motor drive ?
Can I move motor ?
please give me a sample code

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Hi @jinkumak,
with pysoem you should be able to control any EtherCAT actor device, or retrive data from any EtherCAT sensor device.
You could have a look at issue #30 as a starting point, there is an example for a CiA 402 device profile based motor drive.
Please open a new issue for any further discussion.

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