Suggestion:
This will depends on the PLC (sounds an interesting project). If the language used to control the PLC is RFC or CPIC enabled it should work.
As for an example of an RFC enabled function module, the only real difference between that and any other module is that the RFC Enabled radio button is checked in the attributes, and all parameters are passed by Value. It is also a good idea to use strings for your parameters rather than binary data (ie convert your numbers to strings).
To give you some idea of programming from the PLC end, here are some functions in VBA that will point you in the right direction:
Logon to SAP:
***************************************************************************
*
* Function: Logon_To_SAP as Object
*
* Purpose: Logs onto an SAP system using the provided
criteria and returns
*
a connection object to the caller
*
* Entry: System name to log on to as
string
*
Client of system as string
*
User name as string
*
Password as String
*
* Exit: SAP Connection object
*
* Calls:
*
***************************************************************************
*
Function Logon_To_Sap(System As String, Client As String, User As String, Password As String, Router As String) As Object
Dim Sap
As Object
Dim
iUser As String
Dim
iPass As String
Dim
iClient As String
Dim
iPassword As String
Dim
iRouter As String
Dim
iSystem As String
*
Call
Push_Status("Communicating With SAP")
*
* For some reason, this version of SAP changes
the password variable so hard code them here
*
iUser
= User
iPass
= Password
iClient
= Client
iSystem
= System
iRouter
= Router
Set Sap = CreateObject("SAP.Functions")
Sap.Connection.ApplicationServer
= iSystem
Sap.Connection.Client
= iClient
Sap.Connection.SystemNumber
= "10"
Sap.Connection.User
= iUser
Sap.Connection.Password
= iPass
Sap.Connection.Language
= "E"
Sap.Connection.SapRouter
= iRouter
*
If Sap.Connection.logon(0,
iPass <> "") = False Then
Set Sap = Nothing
End
If
Set Logon_To_Sap
= Sap
End Function
And finally, an RFC call using standard and table parameters:
*
***************************************************************************
*
* Function: SAP_Read_Abap_Source
*
* Purpose: Retreives the source code for the specified
Abap Module
*
* Entry: Abap Module Name to read the
source for
*
* Exit: Array of strings containing
the Abap Source code
*
* Calls: Z_GET_CODE
*
*
FUNCTION Z_GET_CODE.
*
*"----------------------------------------------------------------------
*
*"
*
*"Local Interface:
*
*" IMPORTING
*
*" VALUE(I_ABAPNAME) TYPE PROGRAM
*
*" TABLES
*
*" T_SOURCE_LINES TYPE ZSOURCE_LINES
*
*"----------------------------------------------------------------------
*
*
*
Data: t_Source Type Standard Table of Char255,
*
w_Source Type Char255,
*
w_Output Type ZSource_Line.
*
*
*
Read Report i_AbapName into t_Source.
*
Loop at t_Source into w_Source.
*
w_Output-Line = Sy-tabix.
*
w_Output-Source = w_Source.
*
Append w_Output to t_Source_Lines.
*
EndLoop.
*
ENDFUNCTION.
*
Function SAP_Read_Abap_Source(Abap_Name As String) As String()
*
ReDim
Module_Source(0) As String
Dim R3
As Object
Dim
Table_Factory As Object
Dim
Source_Table As Object
Dim
Table_Row As Object
Dim
Exception As Variant
*
Set
R3 = Logon_To_Sap(g_Sys, g_Client, g_User, g_Pass, g_Router)
Call Push_Status("Reading Source For " & Abap_Name)
If Not R3 Is Nothing Then
Set Table_Factory = CreateObject("Sap.TableFactory.1")
Set Source_Table = Table_Factory.NewTable
If Source_Table.CreateFromR3Repository(R3.Connection, "ZSOURCE_LINE", "T_SOURCE_LINES")
= True Then
If R3.Z_GET_CODE(i_AbapName:=Abap_Name, T_Source_Lines:=Source_Table) Then
For Each Table_Row In Source_Table.Rows
Module_Source(UBound(Module_Source)) = Table_Row(2)
ReDim Preserve Module_Source(UBound(Module_Source) + 1) As String
Next Table_Row
End If
End If
End
If
Set Table_Row
= Nothing
Set
Source_Table = Nothing
Set
R3 = Log_Off_Sap(R3)
Call Pop_Status
SAP_Read_Abap_Source = Module_Source()
End Function
Notes:
What are PLCs and how do they work?
PLCs are often defined as miniature industrial computers that contain hardware and software that is used to perform control functions. A PLC consists of two basic sections: the central processing unit (CPU) and the input/output interface system. The CPU, which controls all PLC activity, can further be broken down into the processor and memory system. The input/output system is physically connected to field devices (e.g., switches, sensors, etc.) and provides the interface between the CPU and the information providers (inputs) and controllable devices (outputs).
To operate, the CPU "reads" input data from connected field devices through the use of its input interfaces, and then "executes", or performs the control program that has been stored in its memory system. Programs are typically created in ladder logic, a language that closely resembles a relay-based wiring schematic, and are entered into the CPU's memory prior to operation. Finally, based on the program, the PLC "writes", or updates output devices via the output interfaces. This process, also known as scanning, continues in the same sequence without interruption, and changes only when a change is made to the control program.
