CAN/LIN Measurements (Option AMS) for InfiniiVision Series Oscilloscopes

Introduction

Debug the signal integrity of your CAN and LIN designs faster

The Keysight Technologies inc. InfiniiVision Series digital storage oscilloscopes (DSOs) and mixed signal oscilloscopes (MSOs) offer integrated serial triggering and hardware-accelerated protocol decoding solutions that give you the tools you need to efficiently and effectively debug your embedded automotive or industrial equipment designs. Option AMS provides extended CAN and LIN triggering and decoding in all four-channel DSOs and MSOs. 

Features:

• Integrated serial triggering for testing your CAN and LIN serial buses
• Real-time protocol decode update rates using hardware-accelerated protocol decoding
• Precision differential active probes
• Mixed-signal measurements across analog sensors, serial buses, and digital ECU signals
• Compatible with Segmented Memory option to capture and decode up to 2000 consecutive frames
• Automatic “Search and Navgations” (7000B only)

Enhance your ability to capture random and infrequent error conditions

Keysight’s automotive serial bus options are based on hardware technology to provide real-time protocol decode update rates. Hardware-accelerated decoding enhances your ability to capture random and infrequent error conditions so that you can debug your automotive designs faster. 

The Keysight CAN/LIN option on InfiniiVision Series scopes allows you to trigger on either standard or extended CAN message IDs, including the message ID of a remote transfer request frame. It supports triggering on a data frame, and allows you to specify message IDs, data and data length for filtering messages of interest. Triggering on active error frames as well as non-flagged “form” errors are also supported. 

Decode information for the CAN and LIN buses is time- correlated with each specific digitized packet waveform. To make the information easier to interpret, the decoded serial data is provided in a color-coded format, as shown in Figure 1. With the real-time update of decoded frames, your ability to find random and infrequent signal integrity problems is greatly enhanced. In this particular screen image, we can see that the scope captured and displayed an error frame (ERR) color-coded in red – indicating an error caused by a system glitch coupling into the differential CAN signal. 

Bus quality and efficiency totalize function

In addition to flagging CAN error frames in real-time, Option AMS also provides real-time CAN bus quality and efficiency measurements. The totalize function provides a complete count of all CAN frames, all active error frames (with %), all overload frames (with %), and a measure of bus utilization (in percent), sometimes called “bus load,” as shown in Figure 2. And with Keysight’s 7000B Series oscilloscope, you can also easily search and navigate within the protocol lister display to find and mark particular events of interest with direct time-correlation to the waveform display. 

Segmented Memory captures more frames

The Segmented Memory Option for Keysight’s InfiniiVision series oscilloscopes can optimize your scope’s acquisition memory allowing you to capture more CAN and/or LIN frames using less memory. Segmented memory acquisition optimizes the number of packetized serial communication frames that can be captured consecutively by selectively ignoring (not digitizing) unimportant idle time between frames. And with a minimum 250 picosecond time-tagging resolution, you will know the precise time between each frame.  

Figure 3 shows a CAN bus measurement with the scope setup to trigger on CAN error frames. Using this triggering condition with the segmented memory acquisition mode turned on, the scope easily captures 1000 consecutive CAN error frames for a total acquisition time of 127.3 seconds. After acquiring the 1000 segments/CAN error frames, we can easily scroll through all frames individually to look for physical layer issues that may be inducing these errors. 

Keysight’ s InfiniiVision series oscilloscopes are the only scopes on the market today that can not only acquire segments of up to four analog channels of acquisition, but also capture time-correlated segments on digital channels of acquisition (using an MSO model), along with hardware-based serial bus protocol decoding.

Probe automotive signals with precision – even in environmental chambers

Signal integrity measurements on differential CAN signals require precision differential active probing. Keysight offers a range of differential active probes for various bandwidths and dynamic range applications.

For testing differential CAN signals on the bench or in the field, Keysight recommends either the N2791A, which is a 25 MHz 8-MΩ differential active probe or the N2792A, which is a 200 MHz 1-MΩ differential active probe. 

If you need to connect to DB9-SubD connectors on your differential CAN bus, Keysight also offers the CAN/FlexRay DB9 probe head (Part number 0960-2926). This differential probe head, which is shown in the insert of Figure 5, is compatible with both the N2791A and N2792A differential active probes and allows you to easily connect to your CAN differential bus. 

In addition to testing in a controlled environment, automotive embedded designs based on CAN technology must also be tested under simulated extreme conditions in environmental chambers. These extreme conditions may include testing ECUs and differential serial buses at temperatures exceeding 150° Celsius. Unfortunately, most differential active probes are not rated to operate at these extreme temperatures. 

For extreme temperature testing applications, Keysight recommends the InfiniiMax 1130A Series differential active probe. With the unique electrical and physical architecture of the 1130 Series InfiniiMax active probes, the N5450A extreme temperature cable extension kit can be used to extend and displace the probe’s active amplifier to be outside of an environmental chamber (see Figure 6). With this configuration, InfiniiMax’ passive probe heads can be connected to test points within the chamber with temperatures ranging from -55 to +155 °C.