Python scripts to interface with the PLC

Setting up python environment

• Install Anaconda
• Create a new anaconda enviroment with python 3.7

conda create -n CM09 python=3.7

• Activate the new environment

conda activate CM09

• Install python asyncua to interface with the PLC using OPC UA

pip install asyncua

Getting information on the available variables on the PLC

uals -u opc.tcp://169.254.1.70:4840

Browsing node Node(NumericNodeId(i=84)) at opc.tcp://169.254.1.70:4840

DisplayName                    NodeId                    BrowseName                Value

LocalizedText(Encoding:3, Locale:en, Text:Views) i=87                      0:Views
LocalizedText(Encoding:3, Locale:en, Text:Objects) i=85                    0:Objects
LocalizedText(Encoding:3, Locale:en, Text:Types) i=86                      0:Types

The interesting information is in i=85 (0:Objects)

uals -u opc.tcp://169.254.1.70:4840 -n 'i=85'

Browsing node Node(NumericNodeId(i=85)) at opc.tcp://169.254.1.70:4840

DisplayName                    NodeId                    BrowseName                Value

LocalizedText(Encoding:3, Locale:en, Text:Server) i=2253                    0:Server
LocalizedText(Encoding:3, Locale:, Text:DeviceSet) ns=2;i=5001              2:DeviceSet
LocalizedText(Encoding:3, Locale:, Text:PLC1) ns=1;s=PLC1                   4:PLC1
LocalizedText(Encoding:3, Locale:en, Text:Configuration) ns=6;i=16          6:Configuration

All our variables are in PLC1

uals -u opc.tcp://169.254.1.70:4840 -n 'i=85' -p '4:PLC1'

Browsing node Node(StringNodeId(ns=1;s=PLC1)) at opc.tcp://169.254.1.70:4840

DisplayName                    NodeId                    BrowseName                    Value

LocalizedText(Encoding:3, Locale:, Text:DeviceManual) ns=1;s=PLC1.DeviceManual         2:DeviceManual           ,
LocalizedText(Encoding:3, Locale:, Text:DeviceRevision) ns=1;s=PLC1.DeviceRevision     2:DeviceRevision         ,
LocalizedText(Encoding:3, Locale:, Text:HardwareRevision) ns=1;s=PLC1.HardwareRevision 2:HardwareRevision       ,
LocalizedText(Encoding:3, Locale:, Text:Manufacturer) ns=1;s=PLC1.Manufacturer         2:Manufacturer           , LocalizedText(Encoding:3, Locale:, Text:Beckhoff)
LocalizedText(Encoding:3, Locale:, Text:Model) ns=1;s=PLC1.Model                       2:Model                  , LocalizedText(Encoding:0, Locale:None, Text:None)
LocalizedText(Encoding:3, Locale:, Text:RevisionCounter) ns=1;s=PLC1.RevisionCounter   2:RevisionCounter        , 0  
LocalizedText(Encoding:3, Locale:, Text:SerialNumber) ns=1;s=PLC1.SerialNumber         2:SerialNumber           ,
LocalizedText(Encoding:3, Locale:, Text:SoftwareRevision) ns=1;s=PLC1.SoftwareRevision 2:SoftwareRevision       ,
LocalizedText(Encoding:3, Locale:, Text:Programs) ns=1;s=PLC1.Programs                 3:Programs
LocalizedText(Encoding:3, Locale:, Text:Tasks) ns=1;s=PLC1.Tasks                       3:Tasks
LocalizedText(Encoding:3, Locale:en, Text:MAIN) ns=4;s=MAIN                            4:MAIN
LocalizedText(Encoding:3, Locale:, Text:DeviceState) ns=4;i=20737                      4:DeviceState

All the information is in the MAIN method (ns=4)

uals -u opc.tcp://169.254.1.70:4840 -n 'i=85' -p '4:PLC1','4:MAIN'

Browsing node Node(StringNodeId(ns=4;s=MAIN)) at opc.tcp://169.254.1.70:4840

DisplayName                    NodeId                    BrowseName                Value

LocalizedText(Encoding:3, Locale:, Text:Stepper001) ns=4;s=MAIN.Stepper001    4:Stepper001
LocalizedText(Encoding:3, Locale:, Text:Lamp001) ns=4;s=MAIN.Lamp001          4:Lamp001
LocalizedText(Encoding:3, Locale:, Text:Lamp002) ns=4;s=MAIN.Lamp002          4:Lamp002
LocalizedText(Encoding:3, Locale:, Text:IOPT100) ns=4;s=MAIN.IOPT100          4:IOPT100

We are interested in the IOPT100 (IO for PT100 sensors)

uals -u opc.tcp://169.254.1.70:4840 -n 'i=85' -p '4:PLC1','4:MAIN','4:IOPT100'

Browsing node Node(StringNodeId(ns=4;s=MAIN.IOPT100)) at opc.tcp://169.254.1.70:4840

DisplayName                    NodeId                    BrowseName                        Value

LocalizedText(Encoding:3, Locale:, Text:RPC_Reset) ns=4;s=MAIN.IOPT100#RPC_Reset           4:RPC_Reset
LocalizedText(Encoding:3, Locale:, Text:RPC_SetDebug) ns=4;s=MAIN.IOPT100#RPC_SetDebug     4:RPC_SetDebug
LocalizedText(Encoding:3, Locale:, Text:RPC_SetOutputs) ns=4;s=MAIN.IOPT100#RPC_SetOutputs 4:RPC_SetOutputs
LocalizedText(Encoding:3, Locale:, Text:RPC_Stop) ns=4;s=MAIN.IOPT100#RPC_Stop             4:RPC_Stop
LocalizedText(Encoding:3, Locale:, Text:RPC_SetLog) ns=4;s=MAIN.IOPT100#RPC_SetLog         4:RPC_SetLog
LocalizedText(Encoding:3, Locale:, Text:RPC_Disable) ns=4;s=MAIN.IOPT100#RPC_Disable       4:RPC_Disable
LocalizedText(Encoding:3, Locale:, Text:RPC_Enable) ns=4;s=MAIN.IOPT100#RPC_Enable         4:RPC_Enable
LocalizedText(Encoding:3, Locale:, Text:RPC_Init) ns=4;s=MAIN.IOPT100#RPC_Init             4:RPC_Init
LocalizedText(Encoding:3, Locale:en, Text:cfg) ns=4;s=MAIN.IOPT100.cfg                     4:cfg
LocalizedText(Encoding:3, Locale:en, Text:info) ns=4;s=MAIN.IOPT100.info                   4:info
LocalizedText(Encoding:3, Locale:en, Text:ctrl) ns=4;s=MAIN.IOPT100.ctrl                   4:ctrl
LocalizedText(Encoding:3, Locale:en, Text:stat) ns=4;s=MAIN.IOPT100.stat                   4:stat

We see the RPC calls here that can be used to control the device. The sensors are enabled at the start of the PLC, so we don't need to do something here. The information is in stat.

uals -u opc.tcp://169.254.1.70:4840 -n 'i=85' -p '4:PLC1','4:MAIN','4:IOPT100','4:stat'

Browsing node Node(StringNodeId(ns=4;s=MAIN.IOPT100.stat)) at opc.tcp://169.254.1.70:4840

DisplayName                    NodeId                    BrowseName                           Value

LocalizedText(Encoding:3, Locale:, Text:bLocal) ns=4;s=MAIN.IOPT100.stat.bLocal               4:bLocal                 , False
LocalizedText(Encoding:3, Locale:, Text:nState) ns=4;s=MAIN.IOPT100.stat.nState               4:nState                 , 2  
LocalizedText(Encoding:3, Locale:, Text:nSubstate) ns=4;s=MAIN.IOPT100.stat.nSubstate         4:nSubstate              , 200
LocalizedText(Encoding:3, Locale:, Text:nErrorCode) ns=4;s=MAIN.IOPT100.stat.nErrorCode       4:nErrorCode             , 0  
LocalizedText(Encoding:3, Locale:, Text:nLastCommand) ns=4;s=MAIN.IOPT100.stat.nLastCommand   4:nLastCommand           , 0  
LocalizedText(Encoding:3, Locale:, Text:nRpcErrorCode) ns=4;s=MAIN.IOPT100.stat.nRpcErrorCode 4:nRpcErrorCode          , 0  
LocalizedText(Encoding:3, Locale:, Text:nStatus) ns=4;s=MAIN.IOPT100.stat.nStatus             4:nStatus                , 0  
LocalizedText(Encoding:3, Locale:, Text:sState) ns=4;s=MAIN.IOPT100.stat.sState               4:sState                 , OPERATIONAL
LocalizedText(Encoding:3, Locale:, Text:sSubstate) ns=4;s=MAIN.IOPT100.stat.sSubstate         4:sSubstate              , MONITORING
LocalizedText(Encoding:3, Locale:, Text:sErrorText) ns=4;s=MAIN.IOPT100.stat.sErrorText       4:sErrorText             , OK
LocalizedText(Encoding:3, Locale:, Text:sRPCErrorText) ns=4;s=MAIN.IOPT100.stat.sRPCErrorText 4:sRPCErrorText          , OK
LocalizedText(Encoding:3, Locale:, Text:sStatus) ns=4;s=MAIN.IOPT100.stat.sStatus             4:sStatus                , OK
LocalizedText(Encoding:3, Locale:, Text:sLastCommand) ns=4;s=MAIN.IOPT100.stat.sLastCommand   4:sLastCommand           , NONE
LocalizedText(Encoding:3, Locale:, Text:sLibVersion) ns=4;s=MAIN.IOPT100.stat.sLibVersion     4:sLibVersion            , 1.1.0.1
LocalizedText(Encoding:3, Locale:, Text:sActionDesc) ns=4;s=MAIN.IOPT100.stat.sActionDesc     4:sActionDesc            , ActivityMonitoring
LocalizedText(Encoding:3, Locale:, Text:sEventDesc) ns=4;s=MAIN.IOPT100.stat.sEventDesc       4:sEventDesc             ,
LocalizedText(Encoding:3, Locale:, Text:nCycleCounter) ns=4;s=MAIN.IOPT100.stat.nCycleCounter 4:nCycleCounter          , 822808
LocalizedText(Encoding:3, Locale:en, Text:arrPT100) ns=4;s=MAIN.IOPT100.stat.arrAI            4:arrAI

The values of the PT100 sensors is in arrPT100.

uals -u opc.tcp://169.254.1.70:4840 -n 'i=85' -p '4:PLC1','4:MAIN','4:IOPT100','4:stat','4:arrAI'

Browsing node Node(StringNodeId(ns=4;s=MAIN.IOPT100.stat.arrAI)) at opc.tcp://169.254.1.70:4840

DisplayName                    NodeId                    BrowseName                       Value

LocalizedText(Encoding:3, Locale:, Text:arrAI[0]) ns=4;s=MAIN.IOPT100.stat.arrAI[0]     4:arrAI[0]
LocalizedText(Encoding:3, Locale:, Text:arrAI[1]) ns=4;s=MAIN.IOPT100.stat.arrAI[1]     4:arrAI[1]

These are the two sensors. The temperature we are interested in is the first one.

uals -u opc.tcp://169.254.1.70:4840 -n 'i=85' -p '4:PLC1','4:MAIN','4:IOPT100','4:stat','4:arrAI','4:arrAI[0]'

Browsing node Node(StringNodeId(ns=4;s=MAIN.IOPT100.stat.arrAI[0])) at opc.tcp://169.254.1.70:4840

DisplayName                    NodeId                    BrowseName                                   Value

LocalizedText(Encoding:3, Locale:, Text:nConversion) ns=4;s=MAIN.IOPT100.stat.arrAI[0].nConversion 4:nConversion            , 2  
LocalizedText(Encoding:3, Locale:, Text:lrPar1) ns=4;s=MAIN.IOPT100.stat.arrAI[0].lrPar1           4:lrPar1                 , 0.01
LocalizedText(Encoding:3, Locale:, Text:lrPar2) ns=4;s=MAIN.IOPT100.stat.arrAI[0].lrPar2           4:lrPar2                 , 0.0
LocalizedText(Encoding:3, Locale:, Text:lrPar3) ns=4;s=MAIN.IOPT100.stat.arrAI[0].lrPar3           4:lrPar3                 , 0.0
LocalizedText(Encoding:3, Locale:, Text:nValue) ns=4;s=MAIN.IOPT100.stat.arrAI[0].nValue           4:nValue                 , 2568
LocalizedText(Encoding:3, Locale:, Text:lrValueUser) ns=4;s=MAIN.IOPT100.stat.arrAI[0].lrValueUser 4:lrValueUser            , 25.68

lrValueUser shows the temperature. In our python script, we need to use ns=4;s=MAIN.IOPT100.stat.arrAI[0].lrValueUser

Getting information on the variable types (needed for calling a method)

$ uals -u opc.tcp://169.254.1.70:4840 -n 'i=86' -d 5 2>/dev/null | grep 'i=7 '
        LocalizedText(Encoding:3, Locale:, Text:UInt32) i=7                       0:UInt32                 

To create a UInt variable in python

ua.Variant(0, ua.VariantType.UInt32)