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3. CANopen communication
TPDO (Transmit Process Data Object): Provides status and measurement
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information with a low communication overhead. Usually used to retrieve the
measured data.
EN
The CANopen dictionary contains all data the sensor provides. It consists of multiple
entries with the following properties (in excerpts):
Index: The 16bit object index, usually written in hexadecimal, e.g.: 1000h
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Subindex: Each object may contain up to 255 subobjects. If no subobjects are
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supported a subindex of 0 is used. In case of existing subobjects subindex 0 provides
a UNSIGEND8 value indicating the number of provided subobjects.
Data Type: The data type, e.g.: UNSIGEND32 (unsigned 32 bit integer)
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Access: The permitted dictionary access, e.g.: RW (ReadWrite), RO (Read Only)
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Default Value: The default value of an object after CANopen device initialization
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PDO Mapping: When yes the object may be transmitted by TPDO (depending on
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TPDO configuration, see 3.4.1)
In the following document objects and subobjects are referenced by following
nomenclature: "object.subobject" (e.g. 1A00h.01 means object index 1A00h, subobject
01h). All indices are given as hex numbers.
CANopen devices implement different device profiles, which provide different
funktioniality and object entries.
3.2 Device profile 404
The sensor implements the CANopen devicve profile 404 for measuring devices. This
adds a couple of object dictionary entries, ranging from 6110h to 9149h.
The measurement values are called analog input process values. Mainly they are
provided through the entries 6130h, 7130h and 9130h (Analog input PV).
A couple of objects, like the analog input PV exist in 3 ways, distinguished by the fist
character:
6xxxh The resulting data type is REAL32 (IEE 754)
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7xxxh The resulting data type is INTEGER16
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9xxxh The resulting data type is INTEGER32
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Entries like these are often referred to in a form like x130h, which means 'any kind of
analog input'
3.3 Service data object (SDO)
Service Data Objects are used to access the entries of the transmitters object dictionary.
Therefore the dictionary entries are accessed by index and subindex.
Therefore the master sends a specific request message followed by an reply from the
sensor.
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WIKA special documentation, model MH-4-CAN
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