[etherlab-users] waiting for received frames

[Jeroen Van den Keybus]

Is there anything holding you from just calling ecrt_master_receive() early
as a kind of poll ?

I'm just wondering if the need for receipt notification would e.g. arise
when someone would send an EtherCAT frame A for gathering data and, as soon
as that frame returns, do some calculations and send a second frame B to
apply process outputs, in an attempt to obtain shorter response times ?

J.


2013/11/21 Martin Troxler <martin.troxler at komaxgroup.com>

> Hi
>
> I watched that discussion about the need for a API to wait (poll) for
> received frames. I still don't get it why that is nessessary.
>
> Here is a clarification of how ethercat (process data transfer) works:
> - Process Data should be regarded as idempotent states, which means it
> doesn't matter how many times you read it.
> - it's a kind of huge shift register from the master through all slaves
> and back to the master where each slave (ESC-Chip) manipulates the
> stream of data on the fly.
> - Slaves (i.e. the firmware on microcontrollers) cannot delay the
> transmission of the frame. If there is no new data the ESC simply
> transfers the actual content of its local memory.
> - The frame transmission time is fixed for a given set of slaves and
> depends largely on the domain size and not on how fast the slave's
> microcontroller can update the data.
>
> Regards
> Martin
>
> Note:
>
> This e-mail is for the named person's use only. It may contain
> confidential and/or privileged information. If you have received this
> e-mail in error, please notify the sender immediately and delete the
> material from any system. Any unauthorized copying, disclosure,
> distribution or other use of this information by persons or entities other
> than the intended recipient is prohibited.
>
> Thank You.
> _______________________________________________
> etherlab-users mailing list
> etherlab-users at etherlab.org
> http://lists.etherlab.org/mailman/listinfo/etherlab-users
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.etherlab.org/pipermail/etherlab-users/attachments/20131121/5ff9be07/attachment-0003.htm>