BACnet: Cyclic Reading of a Property
Hardware
- Raspberry Pi as a BACnet server (provides data points)
- CODESYS Control Win V3 as a BACnet client (cyclic reading of the data points)
Requirements for the server and client
Check that the following entries are present in the file CODESYSControl.cfg.
- Including the BACnet component:
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- Including the INI file of the BACnet stack (pay attention to the syntax):
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Requirements for the BACnet server
- Create a "Standard project" and select "CODESYS Control Raspberry Pi SL" as the device.
- Define the target system by means of the Network scan.
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- Insert a "BACnet Server" and a "BACnet Analog Value" object in the device tree:
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- Every device in a BACnet network must have a unique ID. Set this in the tab BACnet Interface Parameters of the "BACnet Server" object.
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Within a device, every instance of a BACnet object type (BACnet Analog Value, BACnet Binary Value, etc.) receives a unique ID. This remains unchanged here as the value "1".
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| Both the instance ID of the device and the instance ID of the object type are reused in the source code of the BACnet client. |
- Adapt the "PLC_PRG" as follows:
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| VAR
xSwitch : BOOL;
lrValue : LREAL := 0.23; |
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| // Numeric simulation |
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lrValue := lrValue + 0.01; |
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ELSE
lrValue := lrValue - 0.01; |
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BACnet_Analog_Value.PresentValue := lrValue; |
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Requirements for the BACnet client (As of BACnet-Version 1.2.0.0)
- Create a "Standard project" and select "CODESYS Control Win V3" as the device.
- Define the target system by means of the network scan (see BACnet server).
- Insert a "BACnet Server" object and rename it to "BACnet_Client"
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Adapt the PLC_PRG POU as follows:
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| VAR
fbReadProperty : BACnet.BACnetClientReadProperty;
xReadExecute : BOOL;
lrReadValue : LREAL;
xInitDone : BOOL := FALSE;
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| IF NOT xInitDone THEN
fbReadProperty.RegisterToServer(BACnet_Client);
fbReadProperty(dwTargetDeviceNumber := 718,
objType := BACnet.CmpBACnet.IEC_BACNET_OBJECT_TYPE.OBJ_ANALOG_VALUE, objInst := 1,
propID := BACnet.CmpBACnet.IEC_BACNET_PROPERTY_ID.PROP_PRESENT_VALUE);
xInitDone := TRUE;
ELSE
fbReadProperty(xExecute := xReadExecute);
IF fbReadProperty.xDone THEN
xReadExecute := FALSE;
lrReadValue := BACnet.GetRealFromContents(fbReadProperty.result);
END_IF
END_IF |
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Requirements for the BACnet client (Up to BACnet-Version 1.2.0.0)
- Create a "Standard project" and select "CODESYS Control Win V3" as the device.
- Define the target system by means of the network scan (see BACnet server).
- Insert a "BACnet Server" object and a "BACnet Client Property Access" object in the device tree.
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- Adapt the "PLC_PRG" POU as follows:
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readPropertyFB : BACnet.ClientReadProperty; |
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readReal : LREAL;
END_VAR |
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| //Simply execute the FB reading out a property |
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readPropertyFB(clientFB := BACnet_Client_Property_Access, |
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dwTargetDeviceNumber := 718, |
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objType := BACnet.CmpBACnet.IEC_BACNET_OBJECT_TYPE.OBJ_ANALOG_VALUE, |
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propID := BACnet.CmpBACnet.IEC_BACNET_PROPERTY_ID.PROP_PRESENT_VALUE); |
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//Start execution and send BACnet-request to BACnet-network |
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IF NOT readPropertyFB.xExecute THEN |
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readPropertyFB.xExecute := TRUE; |
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//Wait for the answer on the request. When xDone is TRUE, an answer has been received. |
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IF readPropertyFB.xDone THEN |
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//Read out the answers contents |
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readReal := BACnet.GetRealFromContents(readPropertyFB.ReadPropertyResult); |
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//Reset FB and also its contents |
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readPropertyFB.xExecute := FALSE; |
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Downloading and starting the projects
BACnet server
- Download the application to the PLC.
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BACnet client
- Download the application to the PLC.
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Reading a device property
If for example general properties of the device be read, then you have to pay attention that the ID of the device number agrees with the object instance.
Example: Reading the revision number of the firmware:
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| readPropertyFB(xExecute := xExecute, |
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clientFB := BACnet_Client_Property_Access, |
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dwTargetDeviceNumber := 718, |
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objType := BACnet.CmpBACnet.IEC_BACNET_OBJECT_TYPE.OBJ_DEVICE, |
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propID := BACnet.CmpBACnet.IEC_BACNET_PROPERTY_ID.PROP_FIRMWARE_REVISION); |
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