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System Architecture for ECU Production

Test

Electronic control unit (ECU) production test systems are essential for validating the manufacturing and

general functionality of embedded controllers in a vehicle. Due to the increase in capabilities of the

modern-day vehicle and the extremely high number of components being produced globally, it can be

difficult to find an adequate production test platform that provides complete test coverage while also

ensuring fast and reliable testing. The NI PXI platform combined with key components from NI Alliance

Partners is designed to meet these demands and equip users with a powerful production test platform.

Throughout this paper, learn about the essential components of an ECU production test platform while

also seeing how they can be combined to create a full production test system designed for ECUs with pin

counts larger than 50, on average.

Figure 1. It is important to understand the signal connectivity of a production test system when

designing a complete rack.

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Figure 2. All of the components from Figure 1 are configured in a physical test system.

Measurement and Stimulus Generation Instrumentation

The NI PXI platform provides automotive engineers with modular, flexible, and powerful instruments for

taking accurate measurements from the device under test (DUT) while also being able to stimulate it

with signals to see how the device responds. With an offering that includes various instruments such as

digital multimeters (DMMs), digitizers, and power supplies, combined with data acquisition and

communication interfaces, engineers around the world can be sure they can achieve full test coverage.

Most automotive production test applications do not need the fastest digitizer on the market, but they

do require a higher density of channels because of the large number of pins that need to be tested. For

these projects, a digitizer like the NI PXI-5105 would be ideal because it has eight simultaneously

sampled channels. In addition, another common requirement is to be able to flash the ECU into a

diagnostic state and communicate with it to make sure the network communication is functioning

appropriately. Depending on the vehicle and the function of the ECU, the network communication

needed varies. Many powertrain ECUs use a reliable network, like high-speed CAN, for flashing and

communication test, which is where an interface like the NI PXI-8513/2 can be used in the PXI chassis.

For body controllers that handle tasks dealing with power seats, windows, or other less safety-critical

tasks, LIN communication is more common and can be tested using the NI PXI-8516 LIN interface card.

Whatever the combination of modules, the NI PXI platform offers unparalleled timing and

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synchronization capabilities to ensure that the test results are precisely correlated and accurate

decisions can be made quicker.

Figure 3. With thousands of PXI instruments, data acquisition modules, and communication interfaces,

the NI PXI platform can be customized as needed for complete test coverage.

In addition, the entire NI PXI catalog of measurement and stimulus generation products can be

combined in countless ways to adjust to new and emerging technologies in the automotive industry. An

example of this is with multimedia and infotainment test where RF signals play a critical role. A vector

signal generator like the NI PXIe-5673E can be used to simulate a GPS or broadcast signal to ensure the

module is receiving and interpreting the data correctly.

View an example NI PXI system configuration for smaller (<50) pin count ECUs

View an example NI PXI system configuration for larger pin count ECUs

An additional key piece of the system is the instrument access panel (IAP). The IAP serves a number of

purposes for the system, with one being a breakout box for connectivity to the PXI instruments

mentioned earlier. Through the use of an IAP, individual PXI instruments can be connected and different

measurements can be switched into the panel to change which pins of the DUT are being measured. The

IAP also converts connectivity of the instruments to the connectivity coming from the DUT pins. For

example, the instrument access panel shown below is from Alliance Partner IRS Systementwicklung

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GmbH. This IAP was designed with ECU production test in mind and has the ability to connect a large

number of instrumentation channels to different DUT pins.

Figure 4. An example instrument access panel from Alliance Partner IRS Systementwicklung GmbH

provides flexible connectivity to NI PXI Instruments.

Pin Switching

After connecting the PXI measurement instruments to the IAP, these instruments now need to be

connected to the pins on the ECU. This is typically done through the NI SwitchBlock. The customizable

hardware design of the NI SwitchBlock makes it easy to create large switch matrices in PXI while

minimizing wiring, simplifying connectivity, and providing a high degree of flexibility for your switching

needs. With the built-in analog bus lines in the NI SwitchBlock backplane, the PXI instruments can take

the appropriate measurements from the DUT pins via the IAP. In addition, output stimulus signals from

PXI modules can also be routed through the IAP and NI SwitchBlock directly to the ECU under test to

simulate a real-world environment.

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Figure 5. The analog bus lines in the NI SwitchBlock backplane provide flexible routing options for signals

to and from the NI PXI chassis and ECU under test.

Test Controller and Software

With the NI PXI platform, the system controller is integrated with the rest of the chassis, thus saving a

significant amount of space inside of the test system rack and allowing for additional instrumentation,

loads, and so on. NI PXI controllers take advantage of the best-in-class processing technology by using

the latest multicore processors combined with necessary peripherals and memory options.

The NI PXI controller can then be used as the brain of the entire system by configuring how each

instrument operates, controlling the switching operations, and communicating with all other devices.

The controller can house the necessary software components for the system, including the integrated

development environment (IDE) used to develop the tests with all of the necessary hardware drivers.

Oftentimes, in large automotive companies, no two test groups are the same and have different

preferences on how they would like to develop their production test systems. With the NI PXI platform

having all NI components that have the same open driver framework, test organizations can then

choose which development environment works best for them and can access all hardware through

similar sockets.

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Figure 6. With embedded controllers, there is no need for an external PC because the complete system is

contained within the PXI chassis.

Another critical item on the system controller is the test management software. NI TestStand is ready-

to-run test management software that is designed to help engineers develop automated test systems

faster with applications like high-volume automotive production test. NI TestStand encompasses the

ability to develop, execute, and deploy test system software. In addition, test sequences that integrate

code modules written in any test programming language can be developed easily. Sequences also

specify execution flow, reporting, database logging, and connectivity to other enterprise systems. The

automotive production test systems also benefit from an easy-to-use operator interface.

Particularly in an industry like automotive, throughput is essential and performing serial tests on one

DUT at a time can be expensive. As a result, automotive engineers are constantly looking to see how

they can reduce their overall test time by performing parallel DUT testing. There are important

considerations to take into account when selecting the right test hardware for testing multiple DUTs at

once since, for example, some ECUs constantly need some specific signal connectivity to remain on and

functioning. However, regardless of how the hardware is set up, the test management software is

extremely important in performing parallel tests because of how it handles hardware resources, test

execution, and test results.

NI TestStand addresses this concern by being fundamentally architected with parallel test in mind. The

software can run multiple threads within one process, which allows it to easily share data between test

sockets, makes hardware synchronization easier, and lowers the overall cost of test through shared

hardware. Some of the key functions within NI TestStand that make it ideal for parallel testing of

automotive ECUs include:

Parallel and batch process models that automatically manage test threads

Configurable synchronization steps to reserve hardware resources

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The ability to detect and report deadlock to help with troubleshooting

The ability to synchronize switching operations with test code

Auto-schedule step reorders tests to improve hardware utilization

Asynchronous result processing

Parallel and batch models include built-in UUT tracking and result processing functionality

Parallel and batch model threads can be suspended and terminated independently

Figure 7. NI TestStand asynchronous result processing allows another DUT test to begin while results are

being processed and keeps track of each result.

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Figure 8. The NI TestStand multithreaded architecture enables common parallel test architectures to

reduce the test time significantly.

Load Switching

The previous portion of this paper focused on components that were all part of the NI PXI platform and

their connection to the instrument access panel. When performing ECU production test, it is necessary

to connect real or simulated loads to certain ECU pins to simulate in-vehicle devices being controlled

and powered from the ECU. However, the loads often require very high current draws from the ECUs

and can cause significant heat dissipation, which makes NI PXI unsuitable for hosting such devices. These

factors mean that having additional load switching capabilities outside of the PXI chassis help to

complete the full production test system.

A flexible, capable solution for this need also comes from Alliance Partner IRS Systementwicklung GmbH.

This solution is designed with ECU production test in mind and provides a modular approach that is well-

integrated with the NI PXI platform. The load mainframe has 28 slots for 6U load cards that vary in

number of channels and can switch up to 50 A of current. The load management system gives the user

the flexibility to switch multiple power supplies to the DUT with voltages as high as 60 V, making it ideal

for the latest developments in cars supporting the new 48 V standard that will be used in a variety of

applications like start-stop technology. The load management system uses load cards that can support

both generic loads on the boards themselves and the switching of real, external loads to the DUT.

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Figure 9. The load management system is a flexible solution able to switch up to 50 A per channel.

Figure 10. A variety of load cards enables load switching customization in a test system.

To measure the current being carried through a particular channel, some load cards are equipped with

shunt resistors or current transducers that are then output from the rear of the mainframe and can be

connected to the analog bus lines of the NI SwitchBlock before passing through the IAP and to NI PXI

measurement devices.

The load switching capabilities can be configured and controlled via a serial communication interface

and are set up through NI Switch Executive, the same software that configures the NI SwitchBlock.

Through the close cooperation and partnership between NI and IRS Systementwicklung GmbH, the user

can configure both the pin switching and load switching in the same powerful software environment.

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System Power

Supplying power to the entire production test system and how backup power will be applied is a critical

piece in designing the system and must take into account what will be in the rack. Providing power to

everything that expects it requires the proper architecture that often involves the use of a power

distribution unit (PDU), universal power supply (UPS), and additional power supplies for varying low

voltage/high current or high voltage/low current options to the DUT.

A typical PDU takes in power from the appropriate outlet, splits the power into three phases, adds

protection at a specified current level, implements control to turn the system on or off, and outputs a

DC voltage. Depending on the layout of the test system, different items can be powered by the three

phases, making sure that the current draw on each phase does not rise above the set limits on the PDU.

The DC voltages can then be brought out to the mass interconnect of the system to provide specific

voltage levels to a DUT, for example.

The handling of a loss of power or undesired situations like surges or power brownouts is also extremely

critical when constructing a system, especially in the automotive industry. Because production is an

around-the-clock operation and production throughput is a key metric to supply electronic components

to millions of cars around the world, any downtime in a test system due to power problems costs

money. For example, one of the main functions of a UPS is to provide power to all or part of the system

when the power goes out. This is often used to at least shut down the system gracefully and without any

major problems. The UPS also does AC to DC conversion, then back to AC to provide clean power to

whatever components of the system it is connected to. For example, if an NI PXI chassis is being used

with several measurement instruments, the UPS can supply clean power to the chassis to ensure proper

measurements. At the same time, most systems have some kind of emergency stop to shut down the

entire system in the case of a problem. It is important to architect the emergency stop capability so that

the right components are shut down in the right order. For example, if a real load or device is connected

to an ECU and the emergency stop button needs to be pushed, you may want to have the ability to shut

down the actual mechanical device before the test rack.

Mass Interconnect

Now that you have covered all of the components within a typical production test system rack, it’s time

to connect all of the instruments, pin switching connections, load switching connections, and overall

system power distribution to the DUT. This is where a mass interconnect solution is required, especially

for higher pin count ECUs. These systems provide long-term reliability and simplified connectivity by

providing a single point of contact for high-channel-count applications. Mass interconnect solutions

comprise two main components: a receiver and an interchangeable test assembly (ITA).

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Figure 11. A mass interconnect solution comprises several components.

The mass interconnect receiver attaches to the PXI measurement and stimulus instrumentation, pin

switching connectivity, power supplies, and load management system while also directing the PXI

modules to a standard set of mass interconnect receiver modules. These connections are established

through high-channel-count cables, printed circuit boards (PCBs), banana cables, and coaxial wiring. The

connectors used on the receiver provide rugged connections to instruments and high-cycle life times.

Low-cost replacement connectors are also available for systems that experience regular ITA cycling.

Figure 12. Example Mass Interconnect Receiver and NI PXI Chassis

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To complete the mass interconnect solution, you need to develop an ITA to provide both a fixture for

your device under test (DUT) as well as the final wiring to your test points. Develop your ITAs so that all

connections required by the DUT are routed through the mass interconnect solution; this includes

power and control signals. Test signals that are designated to pass through the NI SwitchBlock should

physically connect to the appropriate row or column on the ITA portion of the mass interconnect rather

than the receiver. This approach makes it possible to define unique switch configurations for each ITA.

Figure 13. Developing the right ITA for the DUT is critical in completing the mass interconnect solution.

View recommended mass interconnect solutions for the NI SwitchBlock

Selecting a Scalable Platform With High Reliability and Throughput

As automobiles continue to rapidly evolve in ways that have significant impacts on the way vehicles

operate and protect passengers, it is increasingly important that their component production be tested

to the full extent in an efficient way. The NI PXI platform is equipped to provide full test coverage for

current and future automotive ECUs while also lowering test time through parallel test architectures

with NI TestStand.