[etherlab-users] Vendor pre-defined PDO assignment failed

[Keith Rogers]

The Copley Xenus Plus controller I'm working with has two vendor 
pre-defined PDOs (for Rx and Tx) which map the most common elements used 
in motor control. Those PDOs contain what we need, at least to start 
with, so I tried assigning them to their associated sync managers using 
ecrt_slave_config_pdo_assign_add. It failed.

Wireshark and dmesg showed what happened. For whatever reason, ethercat 
master requested the PDO mappings and then apparently initiated the 
process to change or reassign them. The actual failure occurs when EM 
tries to set the number of mappings in the PDO to 0, because the 
register is read only.

Question 1: Why does EM need to know the mappings to assign a PDO to a 
sync manager?

Question 2: What did EM think it was going to remap the vendor assigned 
entries with? Nothing had been provided for that.

Unless I made a mistake, I can only assume EM doesn't provide a 
mechanism to assign fixed entry PDOs to sync managers. The PDO 
assignments in the documentation and examples which use static arrays 
and the wrapper method ecrt_slave_config_pdos works, so I'm not stuck, 
but I thought I'd report the problem I ran into.

Keith Rogers

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