SPI Interface Customization in Automotive ECU Testing
By: CAS DataLoggers
CAS DataLoggers provided the data acquisition solution to an automotive manufacturer in a real-time Hardware-in-
In HIL test applications, individual components are the Device Under Test (DUT) while the rest of the automobile is absent but simulated mathematically. The DUT interacts with all simulated subsystems during the test. In this case, the airbag ECU under test uses a Serial Peripheral Interface (SPI) to communicate. However, SPI is not an all-inclusive standard but is handled differently for each individual application.
The lead test engineer contacted the North American ADwin distributor, CAS DataLoggers, who supplied an ADwin-Pro-II Data Acquisition and Control System (https://www.dataloggerinc.com/
ADwin is widely used in automotive ECU testing applications and for test stand data acquisition and control. Using the ADwin system, users can acquire the analog/digital signals and I/Os of the ECU under test, while the timing of all signals and messages can be evaluated online at microsecond accuracy with an I/O response time of 1 microsecond.
Since SPI sensors don't share a common SPI standard, simulation must be handled individually. The customer provided CAS DataLoggers with the data sheet for their particular ECU. ADwin's German manufacturer, Jager-ADwin, used this information to customize an ADwin PRO-II system to generate the SPI slave interface for this application. Through 'Master Out Slave In' or MOSI, the ECU provides the clock and sends commands to the ADwin which then sends the ECU a given acceleration value in 10-bit resolution as the desired answer. The ADwin includes all signals on the SPI interface into the ECU test run.
Here the ECU's onboard high-g acceleration sensors are surface-mounted on the airbag ECU itself to detect a crash event. Each of these micromechanical sensors are connected to the ADwin, one per analog channel. These single-channel sensors are based on a digital 16-bit SPI interface. During real-world use, these sensors deploy the airbag by detecting the deceleration of the automobile during a crash event.
The ADwin-PRO-II's outputs stimulate the DUT using analog signals and control the acceleration value each sensor receives, which the PRO-II then measures and records. Acceleration is relatively easy to simulate using an ADwin system, which greatly simplifies this HIL automotive ECU testing application.
The PRO-II control system produces the acceleration signal via current stimulation to the ECU's inputs with a current of varying amount. This acceleration value determines whether the airbag deploys or not. In this case, the particular airbag has a 2-ohm resistance. Every current administered below 500mA is considered to be a test current, used to test varying aspects of performance, for example, if the airbag is mounted properly, etc. In contrast, current above 5 amps is termed the 'explosion current' and this verifies if the airbag itself is deploying properly, as it should in a real crash event.
Additionally, the ADwin simultaneously monitors the tested ECU's outputs and evaluates them online via Ethernet in order to verify whether the stimulation and the ECU's response correspond to the specifications.
Users have discovered that the ADwin's fast compile time greatly speeds application development. Before using ADwin, test engineers had to wait hours after programming their application—
ADwin offers test applications a variety of communications options including connection to a PC via Ethernet (USB optional) to begin the test run and exchange results. As mentioned, ADwin can also interface with CANbus. If users require standalone operation, an available boot option allows for fully-functional operation independent of a PC or external computer.
Test Visualization Software
The ADwin software directly connects with Windows without risk of OS crashes and lockups. This software can be used under Windows and LINUX or as a stand-alone data acquisition system. Users are free to develop their test stand application with a full set of available drivers (VB, VC/C++, LabVIEW, TestPoint and more) enabling full integration with other applications and programming languages including MATLAB and SimuLink.
The test team's automotive ECU testing and development significantly benefitted from the ADwin data acquisition and control system. Here a single test system–the ADwin-Pro-II—
thoroughly-tested component which in turn leads to improved airbag safety and a more reliable automobile.
For more information on the ADwin Pro II Data Acquisition and Control System (https://www.dataloggerinc.com/