[etherlab-dev] Alias Addressing

[Gavin Lambert]

Note that this sort of question belongs on the users list, not the dev list.

When you are commissioning a particular network, you first run "ethercat slaves" to view the list of existing slaves on the network.  This will show both their position-based address and their alias-based address.

You can optionally run "ethercat alias" with additional parameters to specify a specific slave (usually using -p alone, but optionally with some combination of -a and -p if you want to reassign the alias of a slave, or use an existing alias as a base position).  This will set the alias of the specified slave, allowing it to be used in alias-based addressing later.

See "ethercat slaves --help" and "ethercat alias --help" for more information.

Giving slaves an alias is optional, but it can be useful where you have a non-linear network or if devices can be reordered without recommissioning.  Either way your application needs to use matching addressing.

>From application code, you use ecrt_master_slave_config() to begin defining the slave configuration.  This works with either position-based or alias-based addressing; see the documentation for that method for more information.

From: Lingjie_Kong at amat.com
Sent: Friday, 1 June 2018 05:35
To: etherlab-dev at etherlab.org
Subject: [etherlab-dev] Alias Addressing

Hi,

I have a question regarding alias addressing. In page 12 of the 1.5.2 ethercat manual, it says that slave position can be specified by position addressing or alias addressing and refer to 7.1.2.

In 7.1.2, it says setting alias address by doing
ethercat alias [option] <alias>


  1.  However, my question is that does this command actually address slave by its alias number and configure network as alias address for all slaves?
  2.  Meanwhile, does etherlab actually support alias address?
  3.  If so, how to address number of slaves by its alias?
  4.  If each slave has different PDO mapping, how to address the PDO mapping for each slave based on alias.

Thanks,

-Lingjie
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