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From Julian Feinauer <j.feina...@pragmaticminds.de>
Subject Re: [S7] String handling
Date Mon, 03 Sep 2018 12:43:12 GMT
Hi Chris,

it is possible, see e.g. https://support.industry.siemens.com/cs/mdm/109755202?c=94063831435&lc=en-WW
or here https://cwiki.apache.org/confluence/pages/viewpage.action?pageId=89070222 (I added
some information in my proposal).

I am against not supporting non-default String sizes as we use them in projects : )
We could do it the way you suggest it, we only have to document it well to avoid confusion
because the TIA syntax is STRING[length].

If I would have to choose between support of array of strings and strings with variables length
I would definitely go for the latter one as I have seen this way more often than arrays of
strings.

Julian


Am 03.09.18, 14:38 schrieb "Christofer Dutz" <christofer.dutz@c-ware.de>:

    Hi Julian,
    
    is it possible to define any String with a size other than 256? I couldn't find this option
in TIA.
    How about not supporting non-default String sizes for now and if we need it to add it
with something like 
    
    STRING(string-length)[array-size]
    
    Cause it's not actually an array of arrays of strings ... 
    
    Chris
    
    
    
    Am 03.09.18, 13:58 schrieb "Julian Feinauer" <j.feinauer@pragmaticminds.de>:
    
        Hi,
        
        thanks for the clarification.
        Is it weird that for me the blinking Christmas tree seems easier to code in assembler
than in TIA? : >
        
        But to the topic, the array thing is fine and we can simply do it as planned.
        The thing I'm unsure with is an array of Strings.
        In the case of non-default length this would be
        
        P#DB1.DBX314.0:STRING[100][1]
        
        which look bad.
        
        Options are:
        a) Do not allow String arrays
        b) Use another string syntax
        c) use another array syntax
        d) use the syntax as above
        
        Personally, I do not like b-d at all is it is way to confusing.
        Is everybody okay a? Or do we have the feeling to "loose" something?
        I think this is a very rare case in reality so for me it would be fine.
        
        Julian
        
        Am 03.09.18, 11:05 schrieb "Christofer Dutz" <christofer.dutz@c-ware.de>:
        
            Hi Julian,
            
            unfortunately my TIA knowledge is very limited ... I manage to create a blinking
Christmas tree, but doing some intense PLC coding is sort of over my head.
            
            However I do manage to be able to check the array question:
            
            It is possible to define an array of Strings. However it looks as if TIA handles
this as syntactic sugar. Cause if I defined an array of Strings, each is 265 bytes long.
            When I access "strvar[0]" this is translated to: P#DB1.DBX314.0
            And if I access "strvar[1]" this is translated to: P#DB1.DBX570.0
            
            I re-did this check with other datatypes such as Bool:
            
            When I access "boolvar[0]" this is translated to: %DB1.DBX48.0
            And if I access "boolvar[1]" this is translated to: %DB1.DBX48.1
            
            And with byte:
            
            When I access "bytevar[0]" this is translated to: %DB1.DBB50
            And if I access " bytevar[1]" this is translated to: %DB1.DBB51
            
            So I assume there is no "array notation" for TIA addresses.
            
            Chris
            
            
            
            Am 03.09.18, 10:20 schrieb "Julian Feinauer" <j.feinauer@pragmaticminds.de>:
            
                Hey Chris,
                
                thank you for the information!
                Yesterday I went through lots of Siemens manuals just to find out that it
gets the more confusing the deeper you go into.
                Could it be that the P denotes a Pointer?
                Because the "#" is usally used for symbolic addressing when I remember correctly.
                
                My aim is to have a clear and good syntax which is as TIAesk as it could be
but on the otherhand easy to understand for all non TIAlers.
                So for me the addresses read like pointers to the start bit (DBX).
                This probably makes sense as a String is not considered an elementary type
in TIA (as its larger than 4 bytes).
                
                So the combined syntax would be:
                P#DB1.DBX314.0:STRING
                Or
                P#DB1.DBX314.0:STRING[100]
                With explicit length information.
                
                A related question is, how does TIA handling referencing to arrays (I think
we agreed to do this as part of this string here).
                Can anyone with TIA access (chris?) check how tia handles this?
                Or should we simply make it similar with 
                P#DB1.DBX314.0:LREAL[10] // Read 10 LREALS starting at offset 314
                
                What do you think?
                
                Julian
                
                Am 03.09.18, 09:47 schrieb "Christofer Dutz" <christofer.dutz@c-ware.de>:
                
                    Hi Julian,
                    
                    so I spun up my TIA and did some String stuff ...
                    
                    Defined 2 Sting variables:
                    
                    Name: 		Data type: 		Offset:		Start value:
                    Hurz1		String			314.0		'Der Wold, das Lamm"
                    Hurz2		String			570.0		'Auf der grünen Wiese"
                    
                    After compiling the memory block (DB1), the offsets were automatically
set.
                    
                    Then I added a CONCAT function to my PLC program and referenced those
two fields as input. Here's what TIA made out of it:
                    Hurz1: 	P#DB1.DBX314.0
                    Hurz2:  P#DB1.DBX570.0
                    
                    Notice the "P#" instead of the "%"? And it seems that the address looks
like a BIT address, as it has the bit offset part set. But just comparing this to all the
others, it seems like all types can have a bit-offset part set, this is just always ".0" for
any non-bit type.
                    
                    Chris
                    
                    
                    Am 02.09.18, 13:03 schrieb "Julian Feinauer" <j.feinauer@pragmaticminds.de>:
                    
                        Hey everybody,
                        
                        I have another question about the semantics we should provide for
reading / writing Strings in the S7 Driver.
                        I have not found an example on how this is handled currently but to
me it looks a bit like a mix of reading the data as “array”, i.e., using the size parameter
on the request (= fixed size string) but handling it as null terminated String.
                        
                        As I have currently no TIA available, can anyone give me the syntax
how Strings are addressed in TIA.
                        I think they were fixed size always and I would prefer to do it that
way.
                        
                        Could anyone who implemented this (or has expertise in this) help
me out a bit?
                        
                        Thanks
                        Julian
                        
                    
                    
                
                
            
            
        
        
    
    

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