Image Processing Reference
In-Depth Information
•
Transducer-independent interface (TII): he TII is the interface between the STIM and
the NCAP. It is specified as an abstract model of a transducer instrumented over digital
communication lines.
TEDS describe node-specific properties, such as the structure and temporal properties of devices and
transducer data. IEEE defines self-contained nodes with the TEDS stored in a memory directly
located at the node. his causes an overhead on the nodes, so the representation of the configuration
information for such a system must be compact. IEEE achieves this goal by providing a large set
of predefined transducer types and nodes based on enumerated information, where identifiers are
associated with more detailed prespecified descriptions (similar to error codes). Although the stan-
dard defines some possibilities to parameterize an instance of a transducer description, this approach
restricts the device functionality expressiveness in a similar way as in EDDL.
22.5.5 Interface File System/Smart Transducer Descriptions
The STD as defined in [] are a method for formally describing properties of devices that follow the
CORBA STI standard (the descriptions themselves are currently not part of the standard).
The STD uses XML [] as the primary representation mechanism for all relevant system aspects.
Together with related standards, such as XML Schema or XSLT, XML provides advanced structuring,
description, representation, and transformation capabilities. It is becoming the de facto standard for
data representation, and has extensive support throughout the industry. Some examples where XML
has already been used for applications in the fieldbus domain can be found in [-].
As the name implies, the STD describe the properties of nodes in the smart transducer network.
The STD format is used for both describing “static” properties of a device family (comparable to clas-
sic datasheets) as well as for devices that are configured as part of a particular application (e.g., the
local STD also contains the local node address). The properties described in STD cover microcon-
troller information (e.g., controller vendor, clock frequency, clock drift), node information (vendor
name, device name/version, node identifiers), protocol information, and node service information
specifying the behavior and the capabilities of a node. In the current approach, a service plays a simi-
lar role as a functional profile (see Section ..) or function block. he functional units align to the
interface model of the CORBA STI standard [].
It is not always possible to store all relevant information outside the node, but by focusing on
reducing the amount of required information on the node to the minimum, extensive external meta-
information can be used without size constraints. The reference to this external information is the
unique combination of series and serial number of the node. The series number is identical for all
nodes of the same type. he serial number identifies the instance of a node among all nodes of a series.
The advantages of this approach are twofold:
•
First, the overhead at the node is very low. Current low-cost microcontrollers provide
internal RAM and EEPROM memory of around bytes. his will not suffice to store
more than the most basic parts of datasheets according to, e.g., the IEEE . standard
without extra hardware like an external memory element. With the proposed description
approach, only the memory for storing the series and serial number is necessary, which
requires bytes.
•
Second, instead of implicitly representing the node information with many predefined
data structures mapped to a compact format, it is possible to have an explicit representa-
tion of the information in a well-structured and easy-to-understand way. A typical host
computer running the configuration and management tools can easily deal with even
very extensive generic XML descriptions. Furthermore, XML formats are inherently easy
to extend, so the format is open for future extensions of transducer or service types.
