TestProNews Q2 - 2005
Integrate TestStand with Databases Using a Test Data Management System
National Instruments
TestStand
test executive and management software is used for developing and deploying automated
test systems used in a variety of applications including product design, validation
and manufacturing test. The TestStand development environment allows you to rapidly
develop and deploy automated test systems that execute test sequences written in
LabVIEW,
LabWindows/CVI, Visual C/C++, Visual Basic .NET,
and C#. With a multithreaded execution engine, TestStand based automated test systems
can be programmed to test a single device or multiple devices in parallel and batch
modes to meet the most demanding test requirements.
A database can be used to capture large volumes of test data generated by automated
test systems and also provide engineers and managers with real-time access to test
results via the company Intranet. A test data management system, or TDM system,
interfaced to a TestStand-based automated test system performs this function. A
TDM system collects, organizes and manages test data generated by TestStand, stores
the data into a database and provides users real-time access to critical data for
parametric test, design validation, defect analysis, quality control, trending and
reporting. This article will explore a typical automated test and TDM system architecture
and present several strategies for interfacing TestStand to a TDM system based on
a relational database that provides enterprise wide access to test results.
|
Figure 1: Typical automated test system and TDM system architecture |
Typical Automated Test System Architecture
A typical automated test system architecture is comprised of three distinct layers:
the test executive, the test logic, and the services layers.
Test Executive Layer
The test executive layer handles test sequencing, coordination, execution, data
logging, and user interface functions. TestStand test executive software is capable
of handling all the requirements of the test executive layer.
Test Logic Layer
The test logic layer contains modular software code necessary to perform test measurements,
comparison to test parameters, evaluate pass/fail criteria and log test results
data. The modular code can be developed in a variety of software
environments including
LabVIEW, LabWindows/CVI, and .NET compliant languages including C#, C/C++, and Visual
Basic .NET. The test logic layer calls only high-level services layers interfacing
to external test, measurement and instrumentation hardware and other applications
such as calibration systems. The test logic layer software should be developed in
a modular fashion and there should be no dependencies on software in the test executive
or services layer. Individual test logic modules should be capable of executing
stand-alone.
Services Layer
The services layer is used to interface and communicate with other measurement hardware,
test instrumentation and data management services necessary to validate functionality
of the device under test. Some examples of services are instruments and databases.
The hardware abstraction layer provides a physical and software connection to measurement
hardware and test instrumentation enabling data communications and commands to be
passed between the test logic and services layers. The hardware abstraction layer
enables features like plug-and-play Interchangeable Virtual Instruments (IVI) and
Virtual Instrument Software Architecture (VISA) compatible measurement hardware
drivers and test instrumentation. The TDM system services layer provides an interface
to application software and databases. The TDM system services layer collects, organizes
and manages test data and allows real-time access to critical data for analysis,
decision support, historical data trending, archiving and reporting. The TDM system
services provides an abstraction layer for communication to the test logic layer
allowing test results data to be written into a database without having to know
anything about the actual database syntax to insert, update, and query test data
in the TDM system database.
Interfacing TestStand to a TDM System
Three common ways to interface an automated test system based on TestStand to your
TDM system include importing test data generated by TestStand ASCII, HTML and XML
reports, a TDM system application programming interface (API) used for TestStand
programmatic interface or by utilizing custom step types that can be configured
in TestStand sequences. These three interface methods are described in more detail
below.
Import Standard TestStand Report Formats
TestStand can generate and output test results reports in three different formats:
HTML, ASCII text, and XML. If you have an existing TestStand application that saves
data using one of the standard TestStand report formats such as ASCII or XML, you
can use a program such as the
Arendar
test data import utility to read, parse, and insert TestStand reports into the TDM
system database.
The import utility can function manually or automatically. With this approach there
is no need to modify existing TestStand sequences. This solution also works for
importing historical test results from existing legacy reports and data from newly
generated reports. Disadvantages of this approach include dependence on TestStand
report formats which might change over time and also can increase the complexity
of the TDM system import utility required to parse the TestStand reports and save
the test results into a database
Call TDMS API with TestStand Module Adapters
A TDM system will most likely include an application programming interface (API)
enabling communication and data exchange between TestStand automated test applications
and the TDM system and database. The API exposes the underlying TDM system database
giving TestStand applications the ability to securely read, write and update test
system configuration parameters and test results data into the TDM system database.
TestStand applications using the appropriate LabVIEW, LabWindows/CVI, Visual Studio
.NET or ActiveX adapters can call the TDM system API directly and store test results
data into the TDM system database. The disadvantage to this approach is that application
source code for existing TestStand adapters must be modified to incorporate the
TDM system APIs required to exchange test data with the TDM system database.
TestStand Custom Step Types
TestStand provides the built-in capability to create and configure custom step types.
Custom step types can be developed that interface with the TDM system API and can
be conveniently accessed from the TestStand sequence editor. Figure 2 displays custom
step types in a TestStand sequence to open, close, map, and save test results data
into the TDM system database using Arendar TDM software. Custom step types like
the ones shown for Arendar TDM system provide a consistent interface in the TestStand
Sequence Editor and allow test engineers to develop a common code base that can
easily be managed and modified if necessary across all TestStand-based automated
test stations.
Process Model
In addition to executing a sequence of test steps, TestStand can also perform common
test system tasks such as recording the device serial number, notifying the operator
of pass/fail status, and logging test results data into a TDM system database. Common
TestStand procedures that define the overall test operation at a high level are
called a process models. Many TDM system functions like saving, opening and closing
database connections are commonly used in almost all test sequences and thus these
common functions can be placed in the TestStand process model. Placing common TDM
system functionality in the TestStand process model will reduce the amount of logic
and coding required in the actual test sequences. This approach is well suited when
standardizing across multiple test stations, test groups and locations because updates
to the process model can be implemented and distributed in to all geographically-distributed
TestStand-based automation test stations quickly.
|
Figure 2: TDM system custom step types used in a TestStand sequence |
Buy Versus Build
A commercial off-the-shelf (COTS) TDM software product from a well-established company
that specializes in automated test and test data management applications is more
cost effective than developing a proprietary test data management system using internal
engineering resources. The additional costs of a proprietary versus COTS-based TDM
system include obtaining the right project team with the required skills and knowledge,
the cost of the actual project development time, and the cost to maintain the proprietary
TDM system after it has been deployed as shown in Figure 3.
One example of a commercial off-the-shelf
TDM
solution is the Arendar Enterprise software from VI Technology. Arendar provides
a comprehensive set of TDM APIs, TestStand custom step types, and TestStand process
models that can easily be integrated into TestStand sequences and applications.
In addition, Arendar provides a standard import utility that can import test results
data directly from TestStand standard XML reports.
|
Figure 3: COTS TDM system time and cost savings versus proprietary TDM system development |
Conclusion
National Instruments TestStand delivers an industry-standard full-featured test
executive and management environment. TestStand manages the sequencing, execution,
and reporting tasks allowing you to focus on the logic necessary to develop and
deploy automated test systems for a wide variety of product design, validation and
manufacturing test applications.
Several options for interfacing TestStand to a TDM system and associated database
include importing test results data using standard TestStand report formats, test
sequence programmatic interface through the TDM system API, custom step types, and
process models. Interfacing TestStand with a TDM system such as Arendar will provide
you with a scalable and cost effective automated test and data management solution
that can be used for design validation and manufacturing test applications.
Ask the Expert
Email questions concerning this article to:
expert.testpronews@vi-tech.com
|
|
|
|
Read about the latest information for integrating automated test systems throughout the enterprise. |
|
|
|
 |
Download PDF |
|
|
