I want to read a text file containing two INT pairs into a two dimension INT array. The text files will be created externally and copied onto the controller when updated. This will be a headless system (no display).

Does anyone have an ST program example of opening and reading a text file? I downloaded an example used in the help file, but it's not very helpful. I have a lot of programming experience with multiple languages but am new to CodeSys and IEC PLCs.

TIA!
Gyz

Originally created by: scott_cunningham

You will need to use the library SysFile and the functions: SysFileOpen, SysFileRead and SysFileClose. Here is a sample view of a ReadFile program. I suggest adding an FB_EXIT() method (see online help) to the ReadFile program which calls SysFileClose - that helps avoid file handles being left open when the system is interrupted... Hope this helps!

HINT: Some hardware platforms do not support AM_APPEND modes (typically flash based memory devices that don't have hard drives/CF cards/SD cards).

PROGRAM ReadFile
VAR CONSTANT
   MAX_BUFFER : __XWORD := 999;
END_VAR
VAR_INPUT
   FileName : STRING := 'c:/test.txt';
END_VAR
VAR_OUTPUT
   Done : BOOL := FALSE;
   ErrCode : SysFile.SYS_FILE_STATUS := SysFile.SYS_FILE_STATUS.FS_NO_FILE;
   Data : ARRAY[0..MAX_BUFFER] OF BYTE;
   BytesRead : __XWORD := 0;
END_VAR
VAR
   pResult : POINTER TO SysFile.RTS_IEC_RESULT;
   FileHandle : SysFile.RTS_IEC_HANDLE;
   pFileData : POINTER TO BYTE := ADR(Data);
END_VAR
//try to open file
FileHandle := SysFileOpen(szFile:= FileName, am:=AM_READ, pResult:=pResult);
//verify found a file
IF FileHandle = SysFile.RTS_INVALID_HANDLE THEN
   //no file found
   ErrCode := SysFile.SYS_FILE_STATUS.FS_NO_FILE;
   Done := TRUE;
ELSE
   //try to read file out
   BytesRead := SysFileRead(hFile:=FileHandle, pbyBuffer:=pFileData, ulSize:=MAX_BUFFER, pResult:=pResult);
   
   //check if actually read any bytes
   IF BytesRead > 0 THEN
      ErrCode := SysFile.SYS_FILE_STATUS.FS_OK;
   ELSE
      ErrCode := SysFile.SYS_FILE_STATUS.FS_NO_FILE;
   END_IF
   Done := TRUE;
END_IF
//close file!!!!
SysFileClose(hFile:=FileHandle);

That was very helpful - thanks!

I have a some questions not answered in the help file that I'd like to ask.

Q1: Is the data read from the file altered in any way, such a stripping off line terminations (cr/lf)?

Q2: Do the Open/Read/Close functions block execution until completed (success or fail), or do I have to set up a loop and wait for them to complete?

Thanks! I really appreciate your help.
Gyz

Originally created by: scott_cunningham

To answer your questions:

Q1: I think the characters are still there for you to parse. You will need to make a small test - I don't 100% remember.

Q2: The open/read/writes are function calls and so they execute and that's it - no need to "wait". Double check how long the execute time is - depending on size of read and hardware platform....

For embedded systems you typically need to read smaller chunks instead of a large file.

Hello,
it seems that the code of scott_cunningham does exactly what I want to do in my application. However, I got error messages in the variable declaration section (e.g. in this row
ErrCode: SysFile.SYS_FILE_STATUS := SysFile.SYS_FILE_STATUS.FS_NO_FILE;):
"Identifier SysFile not defined".
In the program section there the functions from the SysFile are linked to the Sysfile library. I tried to find this library, but it seems to be very well hidden.
My Codesys version is V3.5 and I'm also new in Codesys programming.
Anyone has got a hint for me?
Greetings!
Oliver

OK I found the errors:
1. the SysFile library was not activated. It took me quite a while to locate it. It is within the Data_Server library.
2. after the activation of the Data_server library in my project, I had to relocate the SysFile variables.

Now there are no errors anymore and I can test the functionality of the code

Thanks so far!

Oliver