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Keysight Technologies
Automotive Serial Bus Testing
Using Keysight's InfiniiVision X-Series
and Infiniium S-Series Oscilloscopes




Application Note
Introduction

The primary reason engineers use oscilloscopes to debug and characterize automotive serial buses
such as CAN, LIN, FlexRay, BroadR-Reach, and MOST, is because of an oscilloscope's inherent ability
to characterize the analog quality of these signals. Performing analog characterization using an
oscilloscope is often referred to as "physical layer" testing. Serial bus protocol analyzers are
optimized for performing measurements at the "application layer". Instruments such as these are
focused on providing trace flow of data at a higher abstraction level -- but at the cost of providing
little or no physical layer measurement capability.

This application note will show a few examples of characterizing the performance of various
automotive serial buses. The examples provided use a Keysight Technologies, Inc. InfiniiVision
X-Series and an Infiniium S-Series oscilloscope and illustrate the strength of each platform. Also
included is a summary of recommended probing solutions, and how to select which oscilloscope
platform may best suit your particular automotive debugging and analysis measurement needs.
03 | Keysight | Automotive Serial Bus Testing Using Keysight's InfiniiVision X-Series and Infiniium S-Series Oscilloscopes - Application Note



Decoding and Triggering on CAN, LIN, and FlexRay

Inherently an oscilloscope is designed to the bottom of the scope's display are the Another unique capability of Keysight's
show the quality of analog signals. However decode traces that are time-correlated to InfiniiVision X-Series oscilloscope is hard-
in the case of these buses specifically, just each captured packet (Ch1/yellow trace = ware-based decoding. This means that fast
seeing is often not enough. Many oscillo- CAN bus, Ch2/green trace = LIN bus). The waveform update rates can be maintained
scopes today can be set up to trigger on upper half of the scope's display shows the (up to 1,000,000 waveforms/sec), and decode
specific events to bring into focus the details time-interleaved protocol decode lister/table. update rates are virtually real-time. This
of how these buses communicate. Decoding The time-interleaved lister display shown in enhances the scopes ability to capture random
and triggering on common automotive serial the expanded view in Figure 1(b) is unique to and infrequent communication errors such as
control buses such as CAN, LIN, and FlexRay Keysight InfiniiVision X-Series oscilloscopes. error frames because the scope doesn't have
is essential for identifying and monitoring the Since the lister shows each message to slow down to update the screen.
signal quality of specific frames/messages, received in time-sequence -- whether from
as well as measuring the timing between the CAN bus or the LIN bus -- this makes it
frames. Figure 1(a) shows an example of easier and more intuitive to perform gateway
capturing and decoding a LIN bus and a timing measurements between multi-bus
CAN bus simultaneously using a Keysight transfers of data. Note that this could apply
InfiniiVision 4000 X-Series oscilloscope. At to any two buses, such as CAN1-to-CAN2.




Figure 1(a). Decoding a LIN bus and CAN bus simultaneously using a Keysight InfiniiVision X-Series
oscilloscope.




Figure 1(b). Expanded view for four lines of the protocol decode lister showing the time-sequence of CAN
messages (blue lines) and LIN messages (green lines). Being able to see this level of detail of each mes-
sage sent over the bus makes it much more intuitive to perform timing measurements between buses.
04 | Keysight | Automotive Serial Bus Testing Using Keysight's InfiniiVision X-Series and Infiniium S-Series Oscilloscopes - Application Note



Decoding and Triggering on CAN, LIN, and FlexRay (continued)
Also available in Keysight's InfiniiVision
4000/6000 X-Series, as well as the Infiniium
S-Series oscilloscopes, is symbolic-level
decoding of the CAN bus. These scopes can
also trigger on the symbolic message name
and signal values or encoded states of those
signals.

With the use of a .dbc file, without any
special translation or PC software, more
insight can be provided into the trace flow
information that is normally exclusive to a
protocol analyzer. This capability interprets
the data into meaningful information.
Symbolic-level decoding of the CAN bus is
a standard capability of the CAN trigger and
decode option for each of these oscilloscope
series from Keysight.

Figure 2(a) shows an example of symbolically
decoding a 500 kbps differential CAN bus
using an Infiniium S-Series oscilloscope. In
addition to displaying message and signal
Figure 2(a). CAN symbolic decoding using a Keysight Infiniium S-Series oscilloscope
names along with numerical values with
units, the InfiniiVision X-Series and Infiniium
S-Series are the only scopes on the market
that can also display the status of
state-encoded signals in symbolic format.
Figure 2(b) shows an expanded view of lines
#8 though #10 of the protocol lister of
Figure 2(b). Message "Airbag" and message "ABS" include examples of state-encoded signals.
Figure 2(a). "Armed", "Deployed", "Unlocked",
and "Locked" are all examples of encoded
states. The scope can interpret these encod-
ed states because of the .dbc file that can be
imported directly, ultimately saving the user
in manual translation time.

In addition the Infiniium S-Series oscillo-
scopes can provide flexible ways to view
the decoded information. You even have the
ability to drill-down for a more detailed view
of decoded data at the bit/field boundary
Figure 2(c). Drilling down to an even more detailed view of decoded data is shown here in bit/field
level as shown in the lower pane of the main
boundary level decoding using a Keysight Infiniium S-Series oscilloscope.
screen Figure 2(a), expanded in Figure 2(c).

To learn more about CAN symbolic level
triggering and decode refer to the application
notes listed under related literature at the
end of this document.
05 | Keysight | Automotive Serial Bus Testing Using Keysight's InfiniiVision X-Series and Infiniium S-Series Oscilloscopes - Application Note



Capturing Long Time-spans of Automotive Serial Data

Sometimes it may be necessary to capture
data from automotive serial buses over long
and continuous time-spans, such as pow-
er-up sequences. Unfortunately, all scopes
have limited amounts of acquisition memory,
and that limits the maximum time-span and
number of messages/frames that can be
captured and decoded. Keysight's Infiniium
S-Series oscilloscopes come standard with
50 Mpts of acquisition memory, and can
even be optioned-up to 800 Mpts. This is
the deepest memory available today in any
oscilloscope in this performance category
which allows you to capture and view the
longest continuous time-span of serial
data possible.

But sometimes even 800 Mpts of acquisition
memory may not be sufficient. To effectively
use memory and extend the amount of time
that can be captured selectively, segmented
memory acquisition is available in the
Infiniium S-Series oscilloscopes.
Figure 3. Using Segmented Memory to capture 1000 consecutive CAN bus errors over a 100 second
time-span.
The InfiniiVision X-Series oscilloscopes
come standard with 4 Mpts of acquisition
memory; as well as the segmented memory Also shown in this measurement example To learn more about segmented memory for
acquisition mode. With segmented memory, using segmented memory is the symbolic serial bus applications refer to the application
the scope optimizes available acquisition decode of all 1000 captured messages in the note listed under related literature at the end
memory by selectively capturing multiple and protocol lister display (upper half of scope's of this document.
consecutive occurrences of specific messag- display). The InfiniiVision X-Series are the
es based on the scope's trigger condition. only oscilloscopes on the market today that
can decode all segments -- not just the
Figure 3 shows an example of capturing 1000 selected segment.
consecutive occurrences of just CAN mes-
sages that contain errors (CRC errors, stuffed
bit errors, no acknowledge bit, and flagged
error frames) over a 100 second time-span.
06 | Keysight | Automotive Serial Bus Testing Using Keysight's InfiniiVision X-Series and Infiniium S-Series Oscilloscopes - Application Note



Eye-diagram Mask Testing

Another test that is often used to char-
acterize the physical layer of automotive
serial buses is an eye-diagram mask test.
An oscilloscope eye-diagram provides
a composite measure of the overall
quality of the physical layer in one simple
measurement. Keysight oscilloscopes can
perform eye-diagram pass/fail testing on the
differential CAN bus (InfiniiVision X-Series
only), the differential FlexRay bus, as well as
the differential MOST50 and MOST150 buses
(Infiniium S-Series only). Several different
industry standard masks based on various
test planes and baud rates for each of these
buses can be download for no charge from
the Keysight.com website.

Figure 4 shows an example of a "TP4"
eye-diagram mask test at the input of a Figure 4. An eye-diagram mask test on a FlexRay bus reveals a shifted bit.
FlexRay receiver using an InfiniiVision
X-Series oscilloscope. In this measurement
example, we can see significant edge jitter,
slow rising and falling edges, and a shifted
bit that intersects the pass/fail mask causing
mask test failures.

Figure 5 shows an example of a differential
CAN bus eye-diagram mask test. The appar-
ent jitter displayed in a CAN eye-diagram
is dominated by network propagation delay
from asynchronous nodes transmitting
data from different physical locations in the
network. The Keysight InfiniiVision X-Series
are the only oscilloscopes in the industry that
can perform CAN eye-diagram mask testing.

To learn more about eye diagram mask
testing on automotive serial buses refer to
the application notes listed under related
literature at the end of this document.
Figure 5. CAN eye-diagram mask test using a Keysight InfiniiVision X-Series oscilloscope.
07 | Keysight | Automotive Serial Bus Testing Using Keysight's InfiniiVision X-Series and Infiniium S-Series Oscilloscopes - Application Note



Physical Layer Compliance Testing

For some the newer automotive serial buses
there are specific compliance tests that must
be met. These tests are set up by a standards
body and ensure that all components that
utilize these buses does so in a way that will
work together, thereby providing consistency
between vendors.

Fully automated testing with comprehensive
test reports of the FlexRay (InfiniiVision
X-Series only), BroadR-Reach (Infiniium
S-Series only), and MOST50/150 (Infiniium
S-Series only) automotive serial buses based
on industry standards/specifications is
available on Keysight oscilloscopes. Figure
6 shows an example a FlexRay summary
test report, along with a detailed report of
an isolated one's measurement using an
InfiniiVision X-Series oscilloscope.
Figure 6. FlexRay physical layer compliance test using a Keysight InfiniiVision X-Series oscilloscope.

Figure 7 shows an example summary
report of a test on an automotive MOST150
network using an Infiniium S-Series oscillo-
scope. Although not shown in the document,
the Infiniium S-Series oscilloscope can also
perform similar physical layer compliance
tests on the BroadR-Reach serial bus.




Figure 7. MOST150 physical layer compliance summary test report based a series of automated tests
performed using a Keysight Infiniium S-Series oscilloscope.
08 | Keysight | Automotive Serial Bus Testing Using Keysight's InfiniiVision X-Series and Infiniium S-Series Oscilloscopes - Application Note



Probing Automotive Serial Buses

Let's now look at probing solutions. The
LIN serial bus is a single-ended bus (signal
-to-ground), and a standard 10:1 passive
probe can be used. However, most other seri-
al buses in the automobile are differential,
which means it is measuring between two
different points and will need a differential
probe to accurately capture it. For the
differential CAN and FlexRay buses, Keysight
recommends using the 200-MHz bandwidth
N2818A differential active probe shown in
Figure 8. This probe is compatible with most
models of the Keysight InfiniiVision X-Series
oscilloscopes, and all models of the Infiniium
S-Series oscilloscopes.

The N2818A differential active probe comes
with Keysight's AutoProbe interface that
powers up the active probe and automatically Figure 8. Keysight's N2818A 200-MHz differential active probe for CAN and FlexRay measurement
detects this probe's 10:1 probe attenuation applications. The optional DB9-SubD probe head makes it easy to connect to your differential bus.
factor and input termination impedance (50 ).

Also recommended if your CAN and/or
FlexRay system includes DB9-SubD type
connectors is the CAN/FlexRay DB9 probe
head (part number 0960-2926) shown in the
inset of Figure 8. This probe head makes it
quick and easy to connect to your CAN and/
or FlexRay differential buses.

For the higher bit rate BroadR-Reach and
MOST50/150 measurement applications,
Keysight recommends using the higher band-
width N2750A InfiniiMode Series differential
active probes (1.5 GHz to 6 GHz bandwidth
models) shown in Figure 9. The InfiniiMode
Series probe allows you to view not only
the differential signal, but you can also set
it up to show each side of the differential
bus relative to ground, as well as show the
common mode of the bus -- without ever
moving probe connections.
Figure 9. Keysight's N2750A InfiniiMode Series differential active probe for
The table on the right summarizes MOST50/150 and BroadR-Reach measurement applications.
recommended probes for each automotive
serial bus.
Standard 10:1 N2818A1 200-MHz N2750A 1.5-GHz
single-ended differential differential
passive probe active probe active probe
LIN
CAN
FlexRay
BroadR-Reach
MOST50
MOST150
1. The N2818A is not compatible with Keysight's InfiniiVision 2000 X-Series models. If using an
InfiniiVision 2000 X-Series oscilloscope for differential CAN bus measurement applications,
the 25-MHz bandwidth N2791A or the 200-MHz bandwidth N2792A differential active probe
are recommended.
09 | Keysight | Automotive Serial Bus Testing Using Keysight's InfiniiVision X-Series and Infiniium S-Series Oscilloscopes - Application Note



Choosing the Right Oscilloscope Platform for Your Automotive Measurements

So which oscilloscope platform from optimized for debugging the physical layer also provide the deepest memory in the
Keysight best fits your automotive serial of CAN, LIN, and FlexRay serial bus designs oscilloscope industry with 50 Mpts of
bus measurement needs; the InfiniiVision with Keysight's fourth-generation MegaZoom standard memory and up to 800 Mpts of
X-Series or the Infiniium S-Series? This technology. This Keysight-proprietary tech- optional acquisition memory. This platform
depends on your oscilloscope performance nology provides the fastest waveform update is based on a Windows operating system
requirements (bandwidth, sample rate, and rates in the oscilloscope industry (up to that has been optimized for advanced
memory depth), automotive measurement 1,000,000 waveforms per second) so that you waveform analysis of automotive system
requirements (serial trigger and decode can capture infrequent transients -- which designs. Besides supporting CAN, LIN, and
only or compliance testing), your use-model are common and inherent in automotive FlexRay serial bus analysis and triggering,
(debug or analysis), and your budget. electrical systems. The InfiniiVision X-Series the Infiniium S-Series oscilloscopes also
oscilloscopes also begin at very low support compliance test options for the
The Keysight InfiniiVision X-Series price-points. BroadR-Reach and MOST50/150 serial
oscilloscopes come in various models with buses based on published industry physical
bandwidths ranging from 70 MHz up to The Keysight Infiniium S-Series oscilloscope layer standards.
6 GHz bandwidth. This platform is based on provides up to 8 GHz bandwidth with
a real-time operating system that has been sampling up to 20 GSa/s. These scopes




The Keysight InfiniiVision 6000 X-Series oscilloscope. The Keysight Infiniium S-Series oscilloscope.
10 | Keysight | Automotive Serial Bus Testing Using Keysight's InfiniiVision X-Series and Infiniium S-Series Oscilloscopes - Application Note


The following table summarizes the features of Keysight's various automotive options in InfiniiVision X-Series and Infiniium S-Series oscilloscopes:


InfiniiVision InfiniiVision InfiniiVision 4000 InfiniiVision Infiniium
2000 X-Series 3000 X-Series X-Series 6000 X-Series S-Series
Oscilloscope specifications
Bandwidth 70