Automotive Ethernet Testing

Automotive Ethernet Testing

Achieving Reliability and Interoperability

Learn how to:

Validate operation
Troubleshoot problems
Test for compliance to standards
Use Signal Separation for Automotive Ethernet Testing

ADAS, smart safety systems, and human to machine subsystems generate vast amounts of data to transport throughout a vehicle. Furthermore, requirements for greater integration between vehicle subsystems are driving fundamental architectural changes: moving from simple ring networks to more complex topologies, including gateways connected to a backbone.

Automotive Ethernet stems from proven IT technology and serves the needs for both capacity and integration. Unlike non-automotive Ethernet, the automotive bus uses unshielded, single twisted-pair cabling designed for lower weight and cost. It uses PAM3/PAM4 modulation to achieve high data rates and reliability.

Automotive in-vehicle networks can consist of a variety of standards and speeds depending upon the specific application and requirements. Ninety percent of in-vehicle network communications in a car operates below 10 Mbps. Low speed CAN/CAN-FD, LIN, FlexRay, SENT, PSI5, and CXPI standards work up to 10 Mbps. Newer applications such as autonomous cars and connected vehicles require much faster in-vehicle network, so the IEEE introduced IP-based Automotive Ethernet 100BASE-T1 (P802.3bw) , Multi-Gigabit Ethernet (IEEE 802.3ch), 1000BASE-T1 (802.3bp) and 10BASE-T1S (IEEE 802.3cg) standards.

To extend the speed, coverage and breath of IP-based In-vehicle network standards, IEEE recently introduced the Multi-Gigabit Ethernet (IEEE 802.3ch) standard which can operate at 2.5Gbps, 5Gbps and 10Gbps with PAM4 encoding scheme.

To ensure the interoperability of hardware and assure reliable vehicle operation in diverse operating conditions, strict constraints are placed on signal levels, noise, and clock characteristics. The testing techniques specified by the standards, although well-established for stationary Ethernet networks, have created new design challenges for many automotive engineers accustomed to working with slower serial buses like CAN and LIN.

Validating your design

Once a prototype network device is built up, it’s time to ‘bring up’ the design and characterize it to make sure it’s within specification.

Tektronix oscilloscopes are an invaluable tool for bringing up and characterizing your Automotive Ethernet design.

Complete characterization under different use cases with advanced measurements and analysis tools
Automated measurements such as amplitude and time measurements, along with statistical analysis and histograms, are a good place to start to check signal quality
Eye diagrams are the fastest way to evaluate PAM3 signaling for noise and signal integrity issues
Jitter analysis tools provide complete profiles of master/slave clock jitter including Time Interval Error (TIE), and cycle-to-cycle, Rj/Dj measurements

Eye diagrams are the best way to view complex PAM3 waveforms

Speed debugging and troubleshooting

It’s to be expected that in complex networks systems or components sometimes fail, requiring speedy debug to root cause. Automotive Ethernet’s higher data rates and embedded clocking are sensitive to noise and power variations.

Engineers, used to evaluating waveforms as part of their troubleshooting procedure, often find the PAM3 signals more difficult to debug. Also, since automotive Ethernet is a bi-directional bus it can be more challenging to capture the exact signal of interest.

Tektronix oscilloscopes configured with advanced analysis software provide the tools required for quick and effective troubleshooting if you miss the mark on a spec.

TIE and histograms to troubleshoot clock recovery problems
Eye diagrams to quickly evaluate PAM3 signals
Advanced jitter analysis to identify noise sources by determining whether the jitter is random or deterministic
Extended triggering functionality
FFT analysis to isolate sources of interference

Troubleshooting complex systems requires multi-channel measurements and capable signal integrity tools such as FFTs and jitter analysis.

Automated tests such as this Power Spectral Density test, confirm compliance with the standard by comparing results to test limits.

Compliance with confidence

With greater integration of subsystems into networked environments engineers have to provide verifiable, objective evidence that every device is interoperable; that an individual ECU will reliably communicate with any other ECU. Requirements also extend to EMI/EMC and ESD testing.

However, the adoption of more complex, high speed Mbps and Gbps serial technologies can be more challenging to test.

Tektronix has been involved in high-speed compliance testing for many years and is applying this expertise to testing newer technologies in automotive. Compliance solutions include support for 100BASE-T1 (802.3bp^TM) and as well as BroadR-Reach or 100BASE-T1 (802.3bw^TM). The latest compliance solution is for Multi-Gigabit Ethernet (IEEE 802.3ch) and 10BASE-T1S (802.3cg). All adhere to the testing requirements defined by the OPEN Alliance. Tektronix oscilloscopes and spectrum analyzers can also be applied for ESD and EMC testing.

Introducing Signal Separation for Automotive Ethernet Testing

Signal Characterization and Protocol testing of automotive Ethernet can create challenges from design to validation to maintenance. Seeing actual data between ECU#1 and ECU#2, assessing signal integrity in Full Duplex mode and examining Protocol data at the system level without breaking the cable add test complications, time and expense. Tektronix’ unique, patent pending, Signal Separation solution overcomes the shortcomings of current offerings in the market, enabling customers to:

Separate traffic from ECU#1 and ECU#2 in Full-Duplex mode without having to cut cables or make hardware changes to the Ethernet cable
Simultaneously display ECU#1 and ECU#2 Protocol decode data
Perform Protocol decode in Full-duplex mode
Automotive Ethernet PAM3 and Signal Separation Introduction
Automotive Ethernet: See the True Signal