Gavin,
Thanks for your reply. Currently this slave does not support SDOs since it is a 'resource constrained' FPGA based design. Both fast and small, and slow and large PDOs are, unfortunately, on the same slave. I would have liked to stay away from using SDOs in the control process. So currently I'm considering two options: either bring out some form of freely programmable datagram service in the API, or construct a mailbox-like protocol over a limited-size protocol. The latter isn't exactly good for the 'resource constrained' part of my design. J. J. 2013/12/10 Gavin Lambert <gav...@compacsort.com> > How often do you need to access the large value? If it’s at a reasonably > slow rate (and if you have the freedom to change the slave, or at least > unmap the PDO, which it sounds like you do from the below) then you might > want to consider accessing it as an SDO instead. If it’s an array or > record type then you should be able to access it in small enough chunks to > not upset your high-speed domain. (Provided that the slave supports CoE, > of course.) > > > > For the high-speed data, if it’s on a separate slave you could consider > using a separate EtherCAT network for it. If it’s on the same slave then > you might need to either break up access to the large chunk as above, or > batch up multiple values (assuming it’s unidirectional) as in oversampling > so that you can have a slower cycle rate. > > > > *From:* etherlab-dev-boun...@etherlab.org [mailto: > etherlab-dev-boun...@etherlab.org] *On Behalf Of *Jeroen Van den Keybus > *Sent:* Wednesday, 11 December 2013 11:02 > *To:* etherlab-dev@etherlab.org > *Subject:* [etherlab-dev] Large PDOs > > > > Hi, > > > > > > I want to use a single, quite large (1,024 byte) PDO. > > > > Does anyone know how to specify such a large PDO in the XML description > file / SII EEPROM content ? It seems that only base types are allowed as > DataType in a PDO entry (basically any common data type up to 64 bits). > Even if using 64-bit ULINTs, that still means I need 64 PDO entries. That's > very unwieldy, especially since the data only make sense as an array. I > would also like to use a single pointer in IgH master to access it. > > > > Another issue is that there's a second domain of 20 bytes that's being > accessed at 100us intervals. Obviously, the large PDO, already requiring > more than 100us on the line for a data exchange, is going to prevent the > small one from being delivered timely, although the large one only needs to > be exchanged once per second. Is there a common way of solving this > (perhaps splitting the domain transfer ?). > > I was thinking of accessing the large PDO directly (outside whatever is > defined in the XML, directly to a configured SM) and use a series of FPxx > commands to exchange data. Is there a way to do this in IgH master ? > > Thanks, > > J. > > > > > > >
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