[jira] [Commented] (PLC4X-154) Reading LREAL from S7 causes PlcRuntimeException

["Mauro Riva (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/PLC4X-154?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17380504#comment-17380504 ] 

Mauro Riva commented on PLC4X-154:
----------------------------------

Hi Christofer,

I didn't find a typeCode for LREAL. However, using Wireshark, I found that the library [plcpleople/node7|https://github.com/plcpeople/nodeS7] is using BYTE for the typeCode LREAL and asks for 8 bytes and that works. 
 Then, I tried this workaround:
 Due that the typeCode 0x30 (s7.mspec file) makes the PLC to return INVALID_ADDRESS (then it results in a INVALID_DATATYPE), I changed that line to:
{code:java}
['0x0F' LREAL            ['0x08'       , 'X'               , '8'                 , 'REAL'                  , 'null'             , 'IEC61131_LREAL'        , 'false'               , 'false'               , 'true'                 , 'true'                 , 'false'             ]]
{code}
and then I added to the encodeS7Address function (inside S7ProtocolLogic.java) the following section:
{code:java}
if (transportSize == transportSize.LREAL) {
   transportSize = TransportSize.LREAL;
   numElements = numElements * 2;
}
{code}
With those two changes, I can use the library to read LREAL values on an S7-1200/1500. I can submit a PULL request with these lines, it is not a clean solution, but it could work for the types (L-XYZ) that you mentioned above.

> Reading LREAL from S7 causes PlcRuntimeException
> ------------------------------------------------
>
>                 Key: PLC4X-154
>                 URL: https://issues.apache.org/jira/browse/PLC4X-154
>             Project: Apache PLC4X
>          Issue Type: Bug
>    Affects Versions: 0.4.0
>         Environment: S7-1500 PLC
>            Reporter: Sebastian Wiendl
>            Priority: Major
>
> Reading an LREAL in my demo project https://github.com/sewiendl/plc4j-demo/tree/feature/read-lreal causes the following exception:{code}org.apache.plc4x.java.api.exceptions.PlcRuntimeException: Field 'LReal' could not be fetched, response was INVALID_DATATYPE
> 	at org.apache.plc4x.java.base.messages.DefaultPlcReadResponse.getFieldInternal(DefaultPlcReadResponse.java:577)
> 	at org.apache.plc4x.java.base.messages.DefaultPlcReadResponse.getObject(DefaultPlcReadResponse.java:81)
> 	at com.example.plc4jdemo.Main.main(Main.java:39){code}The field was added with {code}                builder.addItem("LReal", "%DB101.DBX110:LREAL");{code}



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