[etherlab-users] Problems with Pdo entry with index 0x0000

Jordi Blanch jordi_blanch at encopim.com
Fri Nov 8 12:37:47 CET 2013

Dear Richard,

yes, we were confusing configuration and mapping. Thank you very much
for your explanation, now I think it's clear for us.

Best regards.

On Fri, 08 Nov 2013 12:31:59 +0100, Richard Hacker <ha at igh.de> wrote:
> You have to add the gaps to the configuration but you cannot map them
> to a variable! I think you are confusing configuration and mapping.
> Configuration is done using ecrt_slave_config_pdos() to inform the
> master how the slave PDO is constructed. This configuration may
> include gaps which are used to align PDO's to natural borders.
> However, gaps can not be mapped to a process variable inside your
> program i.e. with ecrt_domain_reg_pdo_entry(). That means you can not
> access the values in these gaps.
> Thus I was wrong last time. Since ecrt_domain_reg_pdo_entry_list()
> can only access real PDO's (having a non-zero index), the
> functionality inside the master is correct.
> - Richard
> Am 11/06/2013 09:17 AM, schrieb Jordi Blanch:
>> Hello,
>> we thought that it was necessary to add GAPs entries to the list,
>> otherwise the master couldn't calculate the bit offset of the data
>> received from ethercat frames because every ec_pdo_entry_reg_t relates
>> it's data position to the previous ec_pdo_entry_reg_t item, isn't it?
>> Also, I think I remember we already tried not to register GAPs and then
>> we were not receiving the data correctly (but I'm talking from my
>> memory...).
>> Thank you.
>> On Tue, 5 Nov 2013 17:48:03 +0100, Florian Pose <fp at igh.de> wrote:
>>> Hello,
>>> On Tue, Nov 05, 2013 at 04:36:26PM +0100, Richard Hacker wrote:
>>>> I understand your problem when registering gaps. Actually the code
>>>> in the ethercat master does not do the right thing by testing on
>>>> index. Actually it should be testing for reg->bit_position instead.
>>>> I will communicate this with the developer.
>>> sorry Richard. I have to be contradictory. ;-)
>>> Please let me clarify this: There should be no gaps in the list passed
>>> to ecrt_domain_reg_pdo_entry(), because gaps are no actual PDO entries
>>> and can not be uniquely identified via PDO entry index and
>>> subindex, and thus can not be registered.
>>> Note that gaps are perfectly valid in context of the PDO configuration
>>> (see ecrt_slave_config_pdos() and friends).
>>> Best regards,
>>> Florian
>>> _______________________________________________
>>> etherlab-users mailing list
>>> etherlab-users at etherlab.org
>>> http://lists.etherlab.org/mailman/listinfo/etherlab-users
> Mit freundlichem Gruß
> Richard Hacker

Jordi Blanch Carles
Unidad de Ensayo y Control

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