Step7 - Is it possible to transfer data to an Array as a Block Parameter

[RMA]

Another one for Simon! This is related to the BLOCK_DB question in as much as it's the same program. I need to pass over the Cell address in the Cognex Camera where my data is to be found. This address is in Excel form i.e. "G107" and needs to be passed to the camera as a String. I declared an Array with 6 entries as a Parameter (to cope with cell addresses like "AB1234", although 4 Characters will usually suffice). The FB accepted the Array as a parameter but I can't find any way to give the above cell address as a Parameter. Perhaps not surprisingly, a STRING input 'G107' didn't work, but neither did DW#16#47313037.

Is this sort of thing possible? Would it work with a STRING (I thought I was making things easier for the subsequent manipulation by using an Array), or must I separate the Parameters into Column as CHAR or BYTE and Row as INT. This could then easily be strung together inside the FB.

Cheers

Roy

 

[PLucas]

Roy,

Before I offer an explanation of how I handle something similar to what you do, can you explain how this information is passed onto the cameras? Is it via Profibus or serial or another way. Also where are you recieving the cell information into the PLC, is this via OPC or a DB already within the PLC?

Does my questions make sense?

Paul

 

[RMA]

Communication with the cameras is via Ethernet. The commands are in the form of STRINGS which are laid in a Send-Buffer in the Camera programs IDB. The results land back in the Receive-Buffer of the same DB.

The handling of the whole business is a bit complex, but it works OK. Now, however, the customer wants to get some additional information from the camera (the camera program has already been modified accordingly, so rather than muck about with the original camera FB I've taken a copy of it and stripped it to the bare bones and call it in the Step (which was previously an unused Reserve Step) immediately following the camera test.

The input data of the Cell address gets modified from "G107" to "GVG107 CRLF" (GV = Get Value) and this STRING gets sent to the camera.

 

[L D[AR2P#0.0]]

Here is an example of passing an array of chars to a function. The array is declared in static data so you can initialse it there.

FUNCTION FC 1 : VOID
TITLE =
VERSION : 0.1

VAR_INPUT
  CellString : ARRAY  [1 .. 6 ] OF CHAR ; 
END_VAR
BEGIN
NETWORK
TITLE =
	  L	 #CellString[1]; 
	  L	 #CellString[2]; 
	  L	 #CellString[3]; 
	  L	 #CellString[4]; 
	  L	 #CellString[5]; 
	  L	 #CellString[6]; 
END_FUNCTION

FUNCTION_BLOCK FB 2
TITLE =
VERSION : 0.1

VAR
  APieceOfString : ARRAY  [1 .. 6 ] OF CHAR  := ' ', ' ', 'G', 'V', '0', '1'; 
END_VAR
BEGIN
NETWORK
TITLE =pass ann array of chars
	  CALL FC	 1 (
		   CellString			   := #APieceOfString);
	  NOP   0; 
END_FUNCTION_BLOCK

 

[RMA]

Thanks for the Array example, Simon. I suspected it would have to be done that way, but one can always hope for a miracle!

Cheers

Roy