Upcoming star-CAN FD : With the rapid development of various industries, consumers are increasingly demanding the intelligentization of automotive electronics, which has also caused automakers to add more and more electronic control systems to automotive control. Whether it is in the automotive field of traditional cars, new energy vehicles, ADAS, autonomous driving, etc., all of them have spawned higher demand, and the traditional CAN bus can not meet the requirements. Therefore, Bosch has introduced more bandwidth and reliability. The excellent " upgraded" CAN——CAN FD .
| What is "Conformance Testing"
Conformance testing is a testing process used to detect whether components comply with relevant standards to ensure product quality.
In the CAN FD network, the inconsistency of the quality of each node may cause problems such as errors, network failures or network paralysis. Therefore, in order to ensure the normal and safe operation of the CAN FD network, a CAN FD conformance test must be performed.
| CAN FD Conformance Test
If you need to conduct a conformance test on the CAN FD network, you need to follow the following test standards.
Conformance test standards:
· ISO 11898
· ISO 16845
· ISO 15765
· OEM standards
According to the above test standards, the CAN FD conformance test content can be divided into:
· Physical layer conformance test
· Data link layer consistency test
· Application layer conformance testing
| Physical layer conformance test
The physical layer conformance test is mainly to test the resistance characteristics, capacitance characteristics, bus terminal resistance and CAN FD physical level value of CAN FD network nodes, aiming to verify the circuit design, physical level and fault tolerance of CAN FD nodes and systems Sexual performance.
The content of CAN FD physical layer conformance test is shown in the following table (excerpt):
| Test item-terminal resistance test
In the CAN FD network, it is necessary to ensure the continuity of the cable impedance to effectively eliminate the signal reflection in the communication cable. Therefore, in the process of designing the network topology, a 120Ω terminal resistance will be connected to the end of the CAN FD bus. In order to suppress reflections.
The resistance value of the terminal resistor must be within the range of 118Ω~132Ω specified in the ISO 11898 standard. Too large or small resistance will have an adverse effect on CAN FD communication. If the resistance value is too small, the signal amplitude will be too small, which will affect the signal recognition, and the communication will be extremely unstable; if the resistance value is too large, the signal amplitude will be too large, signal overshoot will occur, and the signal falling edge (slow down) time will be caused. It becomes longer, resulting in bit (width) recognition errors.
| Test method:
Use Q-Automation, oscilloscope, multimeter and other test tools for measurement.
| Test connection diagram:
After connecting according to the connection method shown in the figure, use an oscilloscope or a multimeter to measure the resistance of the terminal resistance between CAN_H and CAN_L. The resistance should be within the range specified by the test standard.
| Data link layer conformance test
The main purpose of the data link layer consistency test is to ensure that the communication parameters of the nodes remain consistent, so that the CAN FD network can maintain normal and effective work.
The consistency test content of the CAN FD data link layer is shown in the following table (excerpt):
| Test item-message DLC test
The data code length, namely DLC (Data Length Code), is used to specify the number of bytes in the data field. In the CAN FD network, the number of bytes in the data field MAX is 64 bytes. The encoding rules of DLC are shown in the figure below:
The purpose of this test is to detect that all the messages sent by the DUT of the device under test have the correct DLC.
| Test method:
Use Q-Automation, oscilloscope, CAN FD conformance test box and other test tools for measurement.
| Test connection diagram:
After the connection is successful as shown in the figure, the DUT needs to be powered on to stable communication, trigger the DUT to send a CAN FD message, use the oscilloscope to record all the data frames of the DUT, and observe for more than 1 minute. Compared with the message DLC sent by the DUT, it should be consistent with the one defined in the communication matrix.
| Application layer conformance test
Application layer consistency test verifies the integrity of node communication in the network, including tests on upper layer application protocols, network management functions, and fault diagnosis to ensure the reliability of network communication.
The conformance test content of CAN FD application layer is shown in the following table (excerpt):
| Test item-Busoff recovery strategy test
In order to prevent a node from affecting the communication of other normal nodes due to its own reasons, the CAN FD network has a strict error diagnosis function. When the node is in the Busoff state, the ISO 11898 standard stipulates that the communication can be resumed when 11 consecutive invisible bits are detected 128 times on the bus.
In the actual CAN FD communication bus, it is very easy to satisfy 11 consecutive invisible bits that are monitored 128 times on the bus. However, when the node is in the Busoff state, it is unreliable. If the communication is quickly resumed after 128 consecutive invisible bits are detected 128 times, then the communication will have a higher risk. Therefore, in practical applications, "fast recovery" and "slow recovery" strategies are often used.
| Test method:
Use Q-Automation, oscilloscope, CAN FD conformance test box and other test tools for measurement
| Test connection diagram:
After connecting as shown in the figure, first make the DUT communicate with the test tool normally, clear the TEC and REC of the DUT, and then start the CAN FD conformance test box to interfere, and use continuous interference to interfere with the periodic messages of the DUT to make The DUT enters the Busoff state; the fast and slow recovery time of Busoff is analyzed through Q-Automation.
| CAN FD Conformance Test
In order to avoid the error of manual measurement and realize the automation of CAN FD bus test, Fengqiu launched the CAN FD conformance test system. This system can not only complete the test of the CAN FD network physical layer, data link layer, and application layer, but also The corresponding network management test can be formulated according to customer needs to verify the behavior of network sleep and wake-up and network management. It is an excellent and convenient automated test system.
| Automated testing tool-Q-Automation
Q-Automation is an automated test management software based on ATX, used to test the performance of electronic control units (ECU). Q-Automation is an automated test software that supports the integration of CAN FD physical layer, data link layer, application layer, and network management. It supports more than one hundred conformance test items.
ASAM Automotive Test Exchange (ATX) is a standardized XML format description language used to exchange test data between different test systems. Q-Automation supports the ASAM ATX standard, which facilitates data sharing with other tools.
| CAN FD Conformance Test Box
The CAN FD conformance test box includes digital interference and analog interference, and can perform multiple interferences such as CAN FD bus short circuit, CAN FD bus open circuit, and bus terminal resistance matching on the physical layer. Used in conjunction with the CAN FD conformance test system, it can complete the performance evaluation and verification of the DUT and realize the stability of the network system
Performance, reliability, anti-interference testing and verification.
Using the CAN FD conformance test system can achieve high-quality DUT testing, shorten the test cycle, etc., and generate online test reports, which is convenient for quickly analyzing DUT performance and product bus problems.
