Embedded software has role in test, says Keithley
Embedded script processors and embedded software allow for control of an instrument’s operation locally, rather than running a control program on an external PC and simplifies the process of creating new test routines, writes Ami Teli from Keithley Instruments.
Testing components that go into end-products is becoming ever more challenging with the higher levels of functionality in almost all the electronic products.
Because these devices are changing more frequently than ever, they require new testing routines to characterise and/or confirm their performance.
This can mean that the test instruments used last year for characterising the current-voltage (IV) characteristics of a device may lack the capabilities necessary for this year’s test requirements.
In response new instruments are designed to adapt to take on new test routines. The use of embedded microcontrollers/script processors allows the control of an instrument’s operation locally, rather than running a control program on an external PC and communicating commands to the instrument via GPIB, USB, LXI or other interface.
Supporting this is the use of embedded test software to speed and simplify the process of creating new test routines.
A test script is a collection of instrument control commands and/or program statements. These program statements control script execution and provide facilities such as variables, functions, branching, and loop control.
Because scripts are programs, they are written using a programming language, often Lua, which allows users to create powerful, high-speed, multi-channel tests with significantly reduced development times.
Test scripts can be downloaded into either volatile or nonvolatile memory of an instrument with an embedded script processor to allow the instrument to control itself, independent of the system host controller.
This “local control” approach eliminates communications bus traffic delays that would otherwise slow the process of transferring commands from an external controller to the instrument. Controlling an instrument using an embedded script processor can free up the system controller to interface with other instruments in the rack more frequently, thereby increasing the overall system throughput.
Some instruments with an embedded script processor can even control multiple instruments from a single master unit if they are connected via a high-speed trigger synchronisation/inter-unit communication bus.
A test script runs on the embedded script processor on the master instrument and controls any slave unit(s): one script program controls both the master and any connected slaves. This type of master/slave operation is much faster than sending commands and trigger signals back and forth between the controller and the individual instruments in the test configuration over a traditional communications bus and helps reduce programming complexity.
Figure 1 illustrates how the combination of embedded script processors and a high speed intercommunication bus can speed and simplify parallel testing.
Test advantages of instruments with embedded software
Embedding test software in the instrument itself allows users to start making measurements far sooner than they could if they had to write and debug a test program to run on a PC or even a test script.
For example, Keithley’s embedded Java-based test software for Series 2600B instruments allows users to begin characterizing new devices almost immediately, with no need for software installation or programming, enabling true “plug-and-play” I-V characterisation through any browser, on any computer, from anywhere in the world.
Test engineers can connect these instruments to the internet via a LAN cable, open a browser, type in the instrument’s I.P. address, and begin testing. The resulting data can be downloaded to a spreadsheet program such as Excel for further analysis and formatting, or for inclusion in other documents or presentations.
Instruments that combine the use of an embedded microcontroller with embedded software afford test engineers significantly greater throughput advantages than either capability can provide separately.
The combination of embedded script processors and embedded software in a single test instrument offers test system builders and users important advantages, particularly higher throughput and easier system integration, that can help them keep up with fast-changing device test challenges.
Ami Teli is a marketer at Keithley Instruments