PROGRAM PLC_PRG
var constant
   STATE_IDLE:    byte := 0;
   STATE_CONFIG:    byte := 1;
   STATE_OPEN:    byte := 2;
   STATE_FLUSH:    byte := 3;
   STATE_READ:    byte := 4;
   STATE_READWAIT: byte := 5;
   STATE_CATCHEVENT: byte := 6;
   STATE_CLOSE:    byte := 7;
   STATE_CLOSEWAIT: byte := 8;   
end_var
var   
   ready: bool;   
   step: byte := 1;   
   state: udint;
   result: RTS_IEC_RESULT;
   file : SysFileAsync.SysFileAsyncFB;
   jobparams : SysFileAsync.AsyncJob_Param;
   taskName : string := 'EventTask';
   
   open : SysFileAsync.tSysFileOpen;
   write: SysFileAsync.tSysFileWrite;
   read: SysFileAsync.tSysFileRead;
   close : SysFileAsync.tSysFileClose;
   ulOut : SysFileAsync.RTS_IEC_RESULT;
      
   fileName: string := '/dev/input/event1';
   event: array [0 .. 15 ] of byte;   
end_var
case step of
   
   STATE_CONFIG:
   
      jobparams.TaskParam.pszTaskname    := adr( taskName );
      jobparams.TaskParam.ulTaskPriority    := SysFileAsync.TASK_PRIORITIES.TASKPRIO_IDLE;
      jobparams.TaskParam.ulTaskSleepTime := 10;
      jobparams.TaskParam.phTaskHandle    := SysFileAsync.RTS_INVALID_HANDLE;
      jobparams.TaskParam.ulEndTaskAfterJob := 0;
      
      file.AsyncSetJobParams( SysFileAsync.ASYNCJOB_TASK, 1000000, adr( jobparams ) );
      
      step := STATE_OPEN;
      
   STATE_OPEN:
   
      open.szFile := fileName;
      open.am := SysFileAsync.ACCESS_MODE.AM_READ;
      open.pulOut := adr( ulOut );
      
      file.SysFileOpenAsync( adr( open ), adr( state ), adr( result ) );
      step := STATE_READ;
      
   STATE_READ:
   
      if state = SysFileAsync.ASYNCSTATE_READY or state = SysFileAsync.ASYNCSTATE_ERROR or state = SysFileAsync.ASYNCSTATE_TIMEOUT then
         
         (* The file is correctly opened *)
         read.pbyBuffer := adr( event );
         read.ulSize   := sizeof( event );
         read.pResult   := adr( result);
         read.pulOut    := adr( ulOut );
         State := 0;
         
         file.SysFileReadAsync( adr( read ), adr( state ), adr( result ) );
         
         step := STATE_READWAIT;
      end_if
      
   STATE_READWAIT:
      
      ready := state = SysFileAsync.ASYNCSTATE_READY or state = SysFileAsync.ASYNCSTATE_ERROR or State = SysFileAsync.ASYNCSTATE_TIMEOUT;
      step :=   sel( ready, STATE_READWAIT, STATE_CATCHEVENT );
   
   STATE_CATCHEVENT:
   
      step := STATE_READ;
      
   STATE_CLOSE:
   
      close.pulOut := adr(ulOut);
      file.SysFileCloseAsync( adr( close ), adr( state ), adr( result ) );      
      step := STATE_CLOSEWAIT;
      
   STATE_CLOSEWAIT:
   
      ready := state = SysFileAsync.ASYNCSTATE_READY or state = SysFileAsync.ASYNCSTATE_ERROR or State = SysFileAsync.ASYNCSTATE_TIMEOUT;
      
      (* The file is correctly closed *)
      step :=   sel( ready, STATE_CLOSEWAIT, STATE_IDLE );      
      
   STATE_IDLE:   ;
   
end_case