N5402A Automotive Serial Data Analysis Software for Infiniium 8000 Series Oscilloscopes

Introduction

Features

– Protocol decode of the CAN and FlexRay serial buses

– Extensive search capability of CAN and FlexRay frames

– FlexRay jitter and eye-diagram measurements with automatic mask testing

– FlexRay mask failure analysis using eye unfolding

The event-driven CAN (Controller Area Network) serial bus has become the backbone for communication among many separate controllers, sensors, actuators, and ECUs located throughout automotive and industrial designs. The time-triggered FlexRay serial bus is gaining rapid adoption for more safety-critical and drive-by-wire applications where higher baud rates and a deterministic architecture are required. Software engineers typically use dedicated protocol analyzers for higher-level abstract observation of the data layer information of these buses – but without seeing the physical/signal layer characteristics. Hardware engineers often use traditional oscilloscopes to view the physical layer characteristics of automotive serial bus signals, but without being able to easily decipher protocol level information. The Keysight Technologies, Inc. N5402A Automotive Serial Data Analysis software allows engineers to view both the protocol layer information and physical layer signal characteristics inside a single instrument – the Ininiium oscilloscope.

CAN and FlexRay protocol decode analysis

The N5402A’s Automotive analysis software package extends Ininiium’s ease-of-use advantages to serial data analysis. The dialog box makes the setup process to perform CAN and FlexRay serial decode easy. CAN analysis supports CAN 2.0A and CAN 2.0B compliant messages with user-selectable standard data rates from 10 kHz to 1 MHz. In addition, CAN analysis supports single-ended probing on CAN_H or CAN_L, or differential probing across both CAN_H and CAN_L with the signal type selection box as shown in Figure 1. FlexRay analysis supports user-selectable standard data rates of 2.5 Mbps, 5.0 Mbps, and 10 Mbps. Using the FlexRay setup dialog box shown in Figure 2, you can quickly set up the scope to capture and decode FlexRay frames after entering your system’s baud rate and synchronous cycle time. If you then click Autoset and Trigger On Cycle TSS, the scope will automatically select the optimum sample rate, memory depth, clock recovery method, and triggering to repetitively capture an entire FlexRay cycle while triggering on one unique Transmission Start Sequence (TSS) event.

Listing window with automatic click and zoom

CAN and FlexRay decode analysis features a time-correlated decode trace with tic marks, as well as a listing window view with automatic click and zoom capability. When either CAN or FlexRay decode analysis has been turned on, a sliding tab is available to either show or hide a protocol decode list of all frames that have been captured in an acquisition including the index number and time stamp value of each frame. For CAN signals, the window also shows the Data/Remote/ Error frame type, ID, and data content of each CAN packet in the list. For FlexRay signals, the window shows the frame ID, cycle number, and the payload. With the listing window, you can easily scroll through all decoded serial packets in an acquisition to in particular events of interest in the transmission. The listing window can be in full-screen to see more decoded packets at one time, or in half-screen to see the listing window along with the captured waveforms as shown in Figures 3 and 4. To enable easy correlation between the listing window and waveform display, the listing window highlights those serial packets that are currently being viewed in the waveform display. For instance, if you are viewing five serial packets in the waveform display, the listing window will highlight those five serial packet items in the list. The listing window also features an automatic click and zoom capability so that once a particular packet of interest is found in the list, you can click on it to have the scope automatically zoom into that packet for more detailed waveform analysis. The data in the listing window can be saved to a .csv or .txt file for off-line analysis or documentation purposes.

FlexRay eye pattern and jitter analysis

Eye-diagram measurements have traditionally been performed on oscilloscopes by triggering on an explicit clock signal while accumulating multiple/repetitive overlaid waveforms (ininite persistence) of a data signal.

However, many of today’s serial buses, such as FlexRay, are based on signals with embedded clocks (non-explicit). Creating eye diagram displays on these types of serial buses requires that the scope be able to extract and recover the clock from real-time acquisitions of the signal. The recovered clock is then used to “slice” the waveform into multiple bit segments (Unit Intervals) that are then overlaid – or folded – into an eye-diagram display. With the N5402A option, Keysight’s Ininiium Series oscilloscopes can automatically perform real-time eye-diagram measurements along with pass/ fail mask testing on the differential FlexRay bus. For FlexRay real-time eye measurements, there are a variety of clock recovery algorithms to choose from based on clock rates (2.5 Mbps, 5.0 Mbps, and 10 Mbps) and test plane (TP1, TP2, TP3, and TP4). In addition, you can select clock recovery algorithms from a transmitter’s or receiver’s perspective. When using the receiver clock recovery algorithm, the scope re-synchronizes an ideal/ theoretical clock (10 MHz for 10 Mbps FlexRay) to each Byte Start Sequence (BSS) event of every frame. This creates an eye from a receiver’s perceptive showing you what the receiver “sees” relative to its clock re-synchronization. When using one of the FlexRay transmitter clock recovery algorithms, the scope synchronizes an ideal clock to just the first Byte Start Sequence (BSS) event of each frame. Eyes created using this clock recovery algorithm will show what the transmitter sends which may include possible transmitter timebase drift and inaccuracies relative to the ideal clock rate over an entire frame. This method also provides relative timing information of each BSS event within frames. In addition to specifying bit rates and transmitter or receiver clock recovery, the N5402A’s FlexRay clock recovery algorithms also supports filtering the clock recovery on specific frame IDs and cycle number – including base and repetition. This enables the Ininiium oscilloscope to create eye-diagrams based on specific nodes in your synchronous system.