Characterization and Protocol Analysis of In-Vehicle Serial Bus

Introduction

The Power Control Unit (PCU) is engineered to optimize power management in electric vehicles (xEVs). It encompasses components such as a DC-DC converter, which adjusts battery voltage, and an inverter that converts DC voltage to AC voltage. Although the inverter is responsible for driving the motor, the PCU is critical for overall vehicle performance, influencing aspects like acceleration during startup and regenerative braking efficiency. The Engine Control Unit (ECU) that governs the PCU is equipped with a dedicated microprocessor unit (MPU). This unit gathers diverse data, including vehicle speed, accelerator position, battery level, and motor rotation angle (resolver), from multiple other ECUs integrated within the vehicle via the on-board network using CAN*/CAN FD* communications. The power device operates based on the RAM values, which represent the command speed calculated by the MPU from these parameters.
Subsequently, the motor is driven by three-phase inverter signals under Pulse Width Modulation (PWM) control to achieve the target current. As on-board driving systems for electric and hybrid vehicles evolve, they are increasingly focused on addressing global environmental challenges. Key considerations include reducing size and weight, enhancing battery capacity, improving system efficiency to extend driving range, and ensuring inverter reliability in harsh, noisy environments.
*CAN: Controller Area Network
*CAN FD: CAN with Flexible Data rate

Challenges

The ongoing electrification of automobiles leads to an exponential increase in the number of ECUs, sensors, and control devices, resulting in more diverse and high-speed in-vehicle Local Area Networks (LANs) connecting these components. Consequently, comprehensive evaluations are necessary, ranging from physical layer analysis of in-vehicle LANs to assessments that encompass physical signals, subsystems, and vibrations in finished vehicles. As the electrification and intelligence of automobiles progress, various types of on-board buses are being adopted according to the required levels of control, communication speed, data size, and security. The ability to analyze serial buses of different standards concurrently has become increasingly vital for the development and evaluation of automotive systems.

Solutions Provided by the DLM3000, DLM5000, and IS8000

• Observation and Protocol Analysis of Bus Signal for Up to Four Systems
• Automatic Setup of Serial Buses
• Long-Duration Capturing with Deep Memory
  *Note: 1 Gpts is available with an additional option for the DLM5000HD.
• History Function
• Simultaneous Display of Different Locations with Dual Zoom Function
• CAN Bus Communications Analysis using IS8000

Proposals by the DLM3000 and the DLM5000

Observation and Protocol Analysis of Bus Signal Waveforms Up to Four Systems

They display protocol analysis results in real-time while showing physical layer voltage waveforms of multiple buses captured with triggers. They can perform simultaneous analysis up to four serial buses out of nine types of serial buses: UART/I2C/ SPI/CAN/CAN FD/LIN/FlexRay/SENT/CXPI. A single unit can analyze complex systems using different bus standards.
Logic input can also be utilized for serial bus analysis, such as I2C bus and SPI bus, as well as for observation of the data and control signals and as triggering source.
* Logic inputs also available for I2C/SPI/UART/SENT

Figure 1. Simultaneous analysis of four buses and list display

Automatic Setup of Serial Buses

Configuring bit rates and voltage levels for target buses can be a tedious process. The DLM series features a unique Auto Setup function that automatically analyzes and configures input signals. Even in the absence of prior information regarding bit rates or data formats, this function can significantly reduce setup time.Furthermore, the DLM5000HD enhances this functionality by applying Auto Setup to its captured waveform data, streamlining the setup process and minimizing the risk of misconfiguration.

Figure 2. Example of Auto Setup function

Figure 3. DLM5000HD (12-bit)

Long-Duration Capturing with Deep Memory

The DLM series can capture waveforms for durations of up to 0.2 seconds at a sampling rate of 2.5 GS/s and up to 10 seconds at 50 MS/s (DLM3000/DLM5000). The DLM5000HD extends this capability to 20 seconds at the same 50 MS/s sampling rate.
* Maximum memory of 500 Mpts is available as an optional feature for the DLM3000/DLM5000
* Maximum memory of 1 Gpts is available as an option feature for the DLM5000HD

History Function

This feature automatically saves up to 100,000 captured waveforms in its acquisition memory, allowing for later analysis (up to 200,000 waveforms with the DLM5000HD).
Users can display a specific waveform from the captured set or review all waveforms collectively. The history function facilitates cursor measurement and calculations, enabling retroactive tracing of waveforms that may be challenging to capture with standard triggers.

Additionally, a robust history search function enables easy retrieval of waveforms that meet specific criteria from a large set of stored waveforms. Intuitive on-screen search tools allow users to define rectangular, full-waveform, or polygonal zones to isolate key parts of a waveform. If specific values, such as abnormal voltage levels or pulse widths, have been identified, users can also search directly by waveform parameters for quick access to relevant data.

Figure 4. History search function

Simultaneous Display of Different Locations with Dual Zoom Function

To analyze multi-channel waveforms stored in memory, users may need to enlarge the display both horizontally and vertically for detailed observation. The DLM series includes dedicated zoom keys and a scaling knob, facilitating rapid zooming into the desired locations. The touch screen can also be used to specify the desired area for zooming. This capability allows users to zoom and display two waveforms with differing time axis scales simultaneously. Additionally, the Auto Scroll function enables automatic scrolling of zoom window locations. This functionality is particularly useful for debugging, as it allows simultaneous zooming and displaying of different locations, illustrating the “cause” and “result” of an event at varying magnification ratios.

Figure 5. Simultaneous zooming of two locations

Proposals from the IS8000

CAN Bus Communications Analysis Using

IS8000 enables decoding, frame display, and searching of communication content within CAN bus signal waveforms found in measurement files. It also analyzes signal waveforms obtained from oscilloscopes as well as the ScopeCorder series, facilitating the reanalysis of historical communication signal waveforms and comparisons with other physical quantity measurement data.

Figure 6. Decoding CAN communications using the IS8000

IS8000 supports decoding, listing display, and searching communication content from CAN bus signal waveforms. It is capable of processing CAN bus signal waveforms recorded not only by oscilloscopes but also by the ScopeCorder series or IS8000 itself.

Other Serial Bus Analysis Products

Features of the DL950 ScopeCorder

• Insulated inputs up to 1000 V
• 200 MS/s high-speed sampling
• Various plug-in modules and integrated measurement
• Real-time computations
• High noise resistance
• Trend display of in-vehicle serial bus

Figure 7. DL950 ScopeCorder

Differences of In-vehicle Bus Analysis by Oscilloscopes and by ScopeCorders

There are two types of in-vehicle bus analysis: decoding display and trend display.