Why developers should test their electronics early

Mar 20, 2025

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Test strategies do not only start in production. They should be integrated already during development. With embedded JTAG solutions, prototypes can be reliably validated without firmware and transferred into production.

Testing assemblies is often considered a task for production or the test field. However, even in the development stage, the question arises of how prototypes can be validated. An early test strategy offers independence and flexibility for the developer and facilitates the handover to manufacturing.

Many developers are familiar with the following situation: The first prototype is completed but remains unused for days or weeks until the first firmware is available. When errors occur, it is unclear whether they are due to hardware or software. Troubleshooting delays the project and shifts the production start. This increases the time-to-market, costing time and money. The solution lies in providing developers with tools that allow them to perform software-independent quality assurance early on.

For almost three decades, JTAG/Boundary Scan has established itself as a standardized electrical test procedure (IEEE 1149.x) and paved the way for many other technologies. The manufacturer Göpel electronic has been driving this development from the beginning and offers test and programming solutions for complex assemblies with high-speed data paths under the umbrella technology "Embedded JTAG Solutions."

The concept of "Design-for-Testability" is based on the early integration of testing capabilities into circuit design. This involves strategically placing test points, providing signal lines for efficient testing, and intentionally selecting ICs with boundary scan capability. The earlier these measures are considered, the more comprehensive and efficient the subsequent testing strategy can be.

A central role is played by adhering to design rules that ensure test coverage is as high as possible. If these rules are not followed, the depth of testing can be significantly affected or tests may even become impossible. Software support, such as that provided by "SYSTEM CASCON," helps developers check design-for-testability requirements during layout creation and make necessary adjustments.

Especially in high-speed circuits or miniaturized designs, a well-thought-out test concept can be crucial. Here, JTAG-Boundary-Scan offers the advantage of electrically analyzing even difficult-to-access signals. The early implementation of these testing methods saves costs and time in the long run and significantly increases the quality of the final products.

It has been shown that those who think about testing early reduce costs. The concept of "Design-for-Testability" includes design rules that facilitate testing. If these are ignored, the depth of testing can suffer significantly, or testing may even become impossible. Practical software like "SYSTEM CASCON" supports adherence to these rules. This underscores the importance of planning test creation in an early development phase, as changes after the layout is completed are often difficult and costly.

No one knows the assembly better than its developer. They know every component and are aware of the critical points. Design adjustments to increase test depth can be quickly implemented during the development phase. This optimally designs the assembly for testing.

Even the first prototype can be tested with the same tests as the later series product. This saves costly troubleshooting and accelerates development. By having identical tests for development and production, a consistent test depth is achieved, enabling precise, pin-accurate fault analysis. This significantly facilitates the commissioning of prototypes and pre-series.

In manufacturing by an external service provider, the development-accompanying test strategy serves as an optimal interface. The test archive can be handed over directly, so no extensive coordination on test strategy and scope is necessary. This significantly reduces the effort and costs for the contract manufacturer, as only the appropriate equipment needs to be provided.

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Conventional test systems are often large and expensive, such as bed-of-nails adapters or functional test systems. However, even at the engineer's workstation, a high level of testing can be achieved. A compact Embedded JTAG Solutions Controller like the SCANFLEX II CUBE offers a powerful and cost-efficient alternative.

With this controller, the developer can independently create tests and hand over the assembly for testing in manufacturing. The tools included in "SYSTEM CASCON" facilitate the work by showing, among other things, with the help of a Test Coverage Analyzer, which pins are sufficiently tested and where there is potential for optimization.

The effort for test generation is low, as the required information is already known to the developer: Which components are on the circuit board? How are they connected to each other? The assignment of suitable models is straightforward because each boundary-scan-capable component has a standardized BSDL (Boundary Scan Description Language) model. For non-boundary-scan-capable components, there are also description models, such as for RAMs or driver ICs.

The test system provides the models, while the necessary CAD data usually exists early in the development process. This allows potential problems to be easily resolved and an unfavorable design to be quickly adjusted. The generated tests can be used for the first prototype, ensuring consistent test quality throughout the entire product lifecycle.

If the test bus required for boundary scan is already provided on the assembly as an adaptable interface, for example, via a connector, this interface can also be used for in-system programming. This enables, among other things, the loading of FPGAs or CPLDs as well as the flashing of bootloaders – with significant time and cost savings.

Early planning of tests offers numerous advantages. Prototypes can be tested in series quality even without firmware. In-system programming and testing can be performed via a common interface. This saves development time and shortens the time-to-market. The Embedded JTAG Solutions provide the optimal bridge between development and production. With a flexible controller like the SCANFLEX II CUBE, a future-proof platform is available that also integrates advanced technologies for testing, programming, and emulation, and can be easily transferred to production later. (heh)

*Alexander Labrada Diaz is an Application Engineer for Embedded JTAG Solutions at Göpel electronic.