How to solve CAN bus test problems

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How to solve CAN bus test problems [Copy link]

With the rapid development of the new energy vehicle industry, CAN bus problems are becoming increasingly prominent, and potential bus failures are extremely serious. So, how to ensure the stability of the CAN bus, why do OEMs pay more and more attention to CAN consistency testing? How to solve CAN bus testing problems? CAN conformance testing requires that all nodes in the vehicle CAN network meet the CAN bus node specification requirements, reduce the node differences in the CAN network, ensure the stability of the CAN network environment, and effectively improve the anti-interference ability of the CAN network. Why do OEMs pay more and more attention to CAN conformance testing? 1. Vehicle CAN network architecture In the past, the CAN bus network nodes of traditional vehicles were relatively few, such as instruments, engine ECU, etc. However, with the development of the new energy vehicle industry, the nodes in the vehicle CAN network have become extremely complex. Now the number of CAN nodes inside new energy vehicles has reached 60, which are subdivided into multiple CAN network systems. For example, the body contains nodes such as air conditioning, doors, and navigation, and the safety system contains nodes such as airbags and squibs. 411161 The complex CAN network of the whole vehicle 2. The hazards of inconsistent CAN bus In a complex CAN network, the uneven quality of each node will pose a great safety hazard to the CAN bus network. Usually, the error of one node will affect the normal operation of the entire bus and even cause the paralysis of the entire bus. 1. Bus paralysis. For example, a CAN network contains nodes A, B, and C. The differential voltage at node A is 1.2V, while the differential voltage at node B is 2.0V, and the differential voltage at node C is 1.8V. When the vehicle CAN network works in a strong electromagnetic interference environment, the common mode interference of the environment will crosstalk into the CAN bus, which will affect the differential voltage of node A to below 0.9V, causing the node to flip from the dominant level to the recessive level, which in turn causes node A to fail to work and frequently send error frames. In the CAN bus, although the error frame is not received, it still occupies the bus transmission time, so it causes other normal nodes to delay or fail to send, affecting the normal operation environment of the vehicle CAN bus. Solution: The OEM must require that the operating voltage of nodes A, B, and C must be within 1.8V or even 2.0V, this problem is solved. 411162 Error frame occupies bus 2, inconsistent baud rate causes CAN network system crash Bit time (bit width) and baud rate are the most basic elements of CAN bus communication. Bit time = 1/baud rate, for example, if the baud rate is 500k, the bit time is 2us. Under the same CAN bus sampling frequency, when the bit time of a certain node jitters, that is, the bit time is 1.8us or 2.2us, it will cause the logical judgment of the sampling point to be abnormal, resulting in a bus error and causing the CAN network system to crash. Solution: In the CAN network access stage, if the nodes accessing the network are standardized, the bit time of each node must meet t=2us±3%, then the bit time of the CAN network will be highly consistent, and the problem can be circumvented from the CAN bus physical layer. 411163 Baud rate jitter causes bit time variation 3. Incorrect judgment of dominant threshold level leads to vehicle network failure Generally speaking, the mechanism for judging dominant and recessive status of CAN bus is as follows: when the differential level is greater than 0.9V, it is a dominant level; when it is less than 0.5V, it is a recessive level, and the area between 05V and 0.9V is an uncertain area. However, in the actual network, when the differential level of a node in the CAN bus network is 0.9V, it is still judged as recessive, resulting in a bit logic judgment error, which in turn causes the node to send an error frame, causing the bus to fall into a network failure state. Solution: During the CAN network node admission stage, perform an explicit threshold test on each node and use a voltage source to increase the differential voltage to 0.9V, ensuring that all nodes can be judged as dominant at this differential voltage and stop sending messages, will reduce the occurrence of bus fault problems and reduce the workload of CAN bus network debugging. Therefore, in order to ensure the stability of the CAN bus, it is necessary to perform CAN consistency testing on the entire vehicle network. As the overall designer of the CAN bus network, what are the contents of the CAN consistency test? How to ensure the stability of the CAN bus through the CAN consistency test? III. CAN consistency test content and solution 1. CAN consistency test content In China, most of the OEMs have CAN bus network test specifications, which mainly include the physical layer, link layer and application layer.

Physical layer: The physical characteristics of the communication medium, such as amplitude, edge time, etc., are the most important part.

Link layer: Specifies the arrangement and organization of transmission on the medium, such as the frame structure;

Application layer: Information exchange between users, software, and network terminals, with a lot of customer-defined content.

The physical layer's provisions on the physical characteristics of the medium are mainly derived from the standard ISO 11898, and this part of the standard is highly consistent. As for the link layer and application layer, because the OEMs have different vehicle network designs, their application layer tests are inconsistent.

CAN consistency test content (excerpt) 2. CAN consistency test solution CAN consistency test tools include CAN cards, oscilloscopes, power supplies and other equipment. nt=宋体]bus engineers can only manually build the test platform and conduct tests item by item, mainly through the CAN card to collect message data, and use the oscilloscope to test the waveform, so as to achieve the purpose of testing the bit time, amplitude, bit width, etc. However, the test solution is inefficient. It usually takes 10 hours or even 1 day to complete the entire CAN conformance test project. 4111663, Tektronix CAN Conformance Test Solution Tektronix's automotive bus decode and trigger package provides intuitive automatic decode and trigger functions for common ECU buses such as CAN, CAN FD, LIN and FlexRay.

Most Tektronix oscilloscopes allow users to view multiple buses and multiple control signals simultaneously. Mixed signal oscilloscopes support the use of digital channels for bus decoding, freeing up analog channels for evaluating the quality of other signals. With high channel counts, FlexChannel input channels and large HD displays, the 5 Series MSO is particularly suitable for viewing complex ECU. 411167 ECUs communicate over CAN, LIN and other buses and communicate directly with sensors and actuators. The 5 Series MSO Mixed Signal Oscilloscope provides unprecedented insight into ECU designs, enabling: a. Automotive Bus Packages offer CAN, CAN FD, LIN andFlexRay bus decoding and triggering functions;

b.Up to 8 FlexChannel input channels. Each input channel can be configured as one analog channel and 8 digital channels; c. 15.6” high-definition pinch/slide/zoom touch screen. Easily view multiple buses and multiple signals; 411168 Tektronix MDO4000C Series Mixed Domain Oscilloscopes, 200 MHz to 1 GHz Bandwidth, 4 analog channels, up to 16 digital channels, up to 6 GHz Built-in spectrum analyzer for fast mixed signal debug and EMI diagnostics. 411169 Tektronix MDO3000 Series Mixed Domain Oscilloscopes, 100 MHz to 1 GHz Bandwidth, 2 or4analog channels, up to16digital channels, up to3 GHzbuilt-in spectrum analyzer, highly versatile, suitable for mostECU designs.

As the most professional comprehensive instrument service provider in Northwest China, Antai Testing mainly provides services for Tektronix, Keithley, KEYSIGHT, Fluke, etc. nt], GermanyR&S, ChinaRigol, Taiwanchroma and other well-known international and domestic instrumentation brands, and have in-depth cooperation with Geely Automobile, Shaanxi Automobile Group, BYD and other companies, and can provide customers with matureCANbus test solutions.

6” HD pinch/swipe/zoom touch screen. Easily view multiple buses and multiple signals; 411168 Tektronix MDO4000C Series Mixed Domain Oscilloscopes, 200 MHz to 1 GHz bandwidth, 4 analog channels, up to 16 100 MHz to 1 GHz bandwidth, 2 or 4 analog channels, up to 16 10 digital channels, up to 3 GHz, built-in spectrum analyzer, highly versatile, suitable for most ECU designs. 411170 As the most professional comprehensive instrument service provider in Northwest China, Antai Test mainly deals with Tektronix, Keithley, KEYSIGHT, Fluke, etc. nt], GermanyR&S, ChinaRigol, Taiwanchroma and other well-known international and domestic instrumentation brands, and have in-depth cooperation with Geely Automobile, Shaanxi Automobile Group, BYD and other companies, and can provide customers with matureCANbus test solutions. 6” HD pinch/swipe/zoom touch screen. Easily view multiple buses and multiple signals; 411168 Tektronix MDO4000C Series Mixed Domain Oscilloscopes, 200 MHz to 1 GHz bandwidth, 4 analog channels, up to 16 100 MHz to 1 GHz bandwidth, 2 or 4 analog channels, up to 16 digital channels, up to 3 GHz, built-in spectrum analyzer, highly versatile, suitable for most ECU designs. 411170 As the most professional comprehensive instrument service provider in Northwest China, Antai Test mainly deals with Tektronix, Keithley, KEYSIGHT, Fluke, etc. nt], GermanyR&S, ChinaRigol, Taiwanchroma and other well-known international and domestic instrument brands, and have in-depth cooperation with Geely Automobile, Shaanxi Automobile Group, BYD and other companies, and can provide customers with matureCANbus test solutions.