[etherlab-dev] Large PDOs

Jeroen Van den Keybus jeroen.vandenkeybus at gmail.com
Tue Dec 10 23:01:58 CET 2013


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 ?


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