[etherlab-users] Modifying Domain Data

[Graeme Foot]

Hi,

 

As far as I'm aware the answer is no.  ecrt_domain_process() processes the response from the EtherCAT frame and fills in the domain data.

 

 

However, I have a similar situation and what I'm doing is wrapping the access to the domain data in objects.  On startup I create two extra bits of memory the same size as the domains.  One to use as a cache and one to use as a mask.  Each of the wrapper objects gets pointers to the memory also.

 

When an object needs to read its data you can do something like:

    value = ( ((*(_type *)cacheAddress) &  \

               (*(_type *)maskAddress)) |  \

              ((*(_type *)ecAddress) &     \

               ~(*(_type *)maskAddress)) );\

 

When an object needs to write its data you can do something like:

    *(_type *)cacheAddress = value;         \

    *(_type *)maskAddress  = (_type)~0ull;  \

 

Note: if it's a readonly value then you can just of course access the data directly.

 

 

The inside the ecrt_domain_process(),ecrt_domain_queue() calls I update the domain data with something like:

    cnt             = domainSize;

    uint8_t *data8  = (uint8_t *)domECAddress;

    uint8_t *mask8  = (uint8_t *)domMaskAddress;

    uint8_t *cache8 = (uint8_t *)domCacheAddress;

    for (i = 0; i < cnt; i++)

    {

      if (*mask8 != 0)

      {

        *data8 = ((*cache8) & (*mask8)) | ((*data8) & ~(*mask8));

        *mask8 = 0;

      }

 

      data8++;

      mask8++;

      cache8++;

    }

 

Note: In practice I do the majority of the data as uint64's, then revert to uint8's for the remainder.

 

 

I wouldn't mind hearing how other people deal with the issue.

 

 

Regards,

Graeme.

 

________________________________

From: etherlab-users-bounces at etherlab.org [mailto:etherlab-users-bounces at etherlab.org] On Behalf Of WIEGAND Ralf
Sent: Tuesday, 20 March 2012 01:03
To: etherlab-users at etherlab.org
Subject: [etherlab-users] Modifying Domain Data

 

Hello,

 

i have a problem modifying domain data in my ethercat-app. All the examples provided with the etherlabmaster modify the domain data between ecrt_domain_process() and ecrt_domain_queue(). I have the problem, that I have to modify the domain data outside these functions (in another task), but during ecrt_master_receive() my outputs were overwritten in the domain.

Is there any way to modify the domain data outside the functions ecrt_domain_process() and ecrt_domain_queue() ?

 

 

Regards,

 

Ralf Wiegand






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