[ag-automation] LDI-Interface

[Thomas Rothfuss]

Hi,

Robert Schwebel wrote:
  >
> For the OSADL framework, things will have to be integrated into the C
> code. But anyway, that's a thing we can do a little bit later, when the
> framework itself has stabilized.
> 

The interface is a C interface. See FAPIA.h.

> 
>>I tried to send it but the message body was too big. Carsten Emde will
>>set up some space to put it there.
> 
> 
> You can check it into the SVN repository, for example here:
> 
> https://www.osadl.org/svn/osadl/software/fieldbus-framework/lddi-<timestamp>
> 
> My plan is to collect the existing pieces of code there first, then
> merge everything into a common trunk when it's ready.

I uploaded the whole project into 
https://www.osadl.org/svn/osadl/software/fieldbus-framework/fapia-trunk

> 
> 
>>>What is a "parameter" in your abstraction, for example for CANopen?
>>
>>See comment above.
> 
> 
> I still don't understand it. Ok, there may be "parameters", which are
> key/value pairs. But how do you use it? Can you explain an example for
> a real-world parameter? How is it _used_?
> 
> 

There are two possibilities.

1. The parameter is a hardware address without mapping.
There's a PLC which wants to communicate with the CAN.
The PLC-Process sends the key/value to the CAN-Process.
The CAN-Process interprets the parameter name which is the
address and writes the value direct via the CAN-Driver to
the device.


2. There is a logical device with parameters
The CNC wants to set the parameter "speed" at the "X-axis".
The CNC-Process sets the logical_object_name in the
FAPIACommunication struct to "X-axis". In the FAPIAParameter
struct the parameter_name is set to "speed". In the FAPIAValue
struct the data_value is set.
Now the function fapia_parameter_write_request is called.
FAPIA looks up in the configuration file named fieldbus_conf.xml
where the "X-axis" is located. This is e.g. the "Profinet"-Process.
So the message is sent to the Profinet-Process. This process
does the conversion from the Logical Device Interface (LDI) to
the FDDI.


So the only thing FAPIA has to interpret is the configuration
file to retrieve the destination address.



>>Copyright and Licensing Information for the FAPIA of Homag AG, Germany
> 
> 
> Before even looking at this code we'd have to check if this license is
> compatible with GPL+LinkException.
> 

Well if you look closer to the license of FAPIA you'll determine
that FAPIA is completely free (even more free than GPL ;-)). You
may even use it in commercial software.

See fapia-trunk/doc/FAPIALicense.txt


Thomas