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Programmable logic controllers (PLC) FAQ
DDE and PLCs
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How do I use Excel and DDE to get data out of an Allen Bradley PLC? by chakorules
Posted: 27 Dec 02
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Make sure RS Linx is running and you have created a DDE topic. In our example below, our DDE topic is "M1138".
Using the following code, Open an Excel file and click on Tools then Macro, finally clicking on Visual Basic Editor. This will allow you to write some VBA script to tell Excel what you want to read and where to place the data once read from the PLC.
<<<<<<<<<<<<<<<<<<<BEGIN SAMPLE CODE>>>>>>>>>>>>>>>>>>
Sub Start()
Dim lngRow As Long
Dim varCycle As Variant
Dim varLogging As Variant
Dim varResults As Variant
On Error GoTo Error
'opens a COLD DDE link
RSIchan = DDEInitiate("RSLinx", "M1138")
'assign PLC bit values to VB variant varibles
varLogging = DDERequest(RSIchan, "B3/163")
varCycle = DDERequest(RSIchan, "B3/161")
'close COLD DDE link
DDETerminate (RSIchan)
'check to see if the Cycle bit went to "1" if it did, excute read data
If varCycle(1) = "1" And varLogging(1) = "1" Then
'starts at row 3 of sheet
lngRow = 3
If Range("INDATA!A3").Value > 3 Then
'look up last cell and change position
lngRow = Range("INDATA!A3").Value
End If
'check until end of sheet
For lngRow = lngRow To 65500
'look for next empty cell
If Cells(lngRow, 1) = "" Then Exit For
'write current cell location to sheet INDATA
'rather than writing a loop to search on
'every cycle, by the time the log is at row 21,500
'it could take a long time to search the rows...
Range("INDATA!A3").Value = lngRow + 1
'add 1 to row "x" to check next row
Next
'opens a COLD DDE link
RSIchan = DDEInitiate("RSLinx", "M1138")
'there might be a better way to do this like
'using this somehow ???????? but I don't know how
'data = DDERequest(RSIchan, "f11:0,L7,C7")
'Range("[M1138.xls]LOG!R[x]C1:R[x]C7").Value = data
'read word F8:10 and load into a VB variant variable
f810data = DDERequest(RSIchan, "F8:10")
'read word F8:11 and load into a VB variant variable
f811data = DDERequest(RSIchan, "F8:11")
'read word F8:12 and load into a VB variant variable
f812data = DDERequest(RSIchan, "F8:12")
'read word F8:16 and load into a VB variant variable
f816data = DDERequest(RSIchan, "F8:16")
'read word F8:18 and load into a VB variant variable
f818data = DDERequest(RSIchan, "F8:18")
'read word F8:17 and load into a VB variant variable
f817data = DDERequest(RSIchan, "F8:17")
'read word F8:20 force check #1 and load into a VB variant variable
f820data = DDERequest(RSIchan, "F8:20")
'read word F8:21 force check #2 and load into a VB variant variable
f821data = DDERequest(RSIchan, "F8:21")
'read word F8:22 force check #3 and load into a VB variant variable
f822data = DDERequest(RSIchan, "F8:22")
'read word F8:23 force check #4 and load into a VB variant variable
f823data = DDERequest(RSIchan, "F8:23")
'read word F8:24 max force and load into a VB variant variable
f824data = DDERequest(RSIchan, "F8:24")
'read word F8:25, get PASS or FAIL status from PLC and load into a VB variant variable
varResults = DDERequest(RSIchan, "F8:25")
'close COLD DDE link
DDETerminate (RSIchan)
'write all values to cells
Cells(lngRow, 1).Value = f810data
Cells(lngRow, 2).Value = f811data
Cells(lngRow, 3).Value = f812data
Cells(lngRow, 4).Value = f816data
Cells(lngRow, 5).Value = f818data
Cells(lngRow, 6).Value = f817data
Cells(lngRow, 7).Value = f820data
Cells(lngRow, 8).Value = f821data
Cells(lngRow, 9).Value = f822data
Cells(lngRow, 10).Value = f823data
Cells(lngRow, 11).Value = f824data
'capture time and date stamp into column 8
Cells(lngRow, 13).Value = Now()
'scrolls the screen down automatically
'Range("A" & lngRow + 1).Select
End If
End Sub
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