The inconsistency of the Quality of the CAN bus, errors, cranes, etc., CAN consistency tests have become an important means to ensure the safe operation of CAN networks, which will introduce the fault tolerance test in the CAN bus consistency test.
CAN consistency test content, covering physical layer, link layer, application layer and other test requirements, the testing of fault tolerant performance is mainly at the physical level, through ground wire drift, loss of ground, loss, CAN line interrupt, CAN line Short receipt, the CAN line is shorter to the power supply, the CAN line short circuit and other error state simulations, the overall investigation of the measured node and system work, and the recovery time.
Test principle
Ground wire drift: Using the power to raise the DUT GND, the test bus communication is normal, and the ground wire allowed by DUT drift.
Loss of the ground: Do DUT separately, Test is still working properly within 1 minute.
Power loss: Make DUT to lose the power supply separately, the test bus is disturbed, and the DUT will recover from the DUT after the power supply.
CAN line interrupt: Test in CAN_H for 1 minute, after re-connecting, whether DUT can recover communication. CAN_L is disconnected for 1 minute, and the DUT will be restored to the communication. CAN_H and CAN_L are disconnected at the same time, and the DUT is resembled to recover communication.
The CAN line is short-connected to the ground:
The test is shorted for 1 minute in Can_h, and the DUT can restore communication after recovery;
Test CAN_L to short the ground for 1 minute, and if the DUT can restore communication after recovery;
Test CAN_H and CAN_L simultaneously short circuit for 1 minute, and if the DUT can restore communication after recovery.
The CAN line is shorted to the power cord:
The test is shorted for 1 minute in Can_h, and the DUT can restore communication after recovery.
Test CAN_L for 1 minute of the power supply, after restoring, whether the DUT can recover communication;
Test CAN_H and CAN_L simultaneously on the power supply for 1 minute, and if the DUT can recover communication after restoring.
CAN_H is shorted to CAN_L: Test CAN_H, CAN_L short circuit for 1 minute, and if the DUT can recover communication after restoring.
Test wiring
This test uses the Canscope-Pro and the Canscope-Stressz expansion board, program-controlled power. When DUT is powered on, it has been sent to send CAN packets, which is convenient for testing. Its black table pen (ground) is also common to the DUT CAN transceiver. The oscilloscope hook is enabled, that is, the oscilloscope is not enabled, and the CANSCOPE's CAN interface is electrically isolated. Test connection as shown below.
Figure 1 fault tolerance performance test wiring diagram
Testing process
Ground wire drift:
If the CAN interface of the DUT is isolated, the program-controlled supply voltage + - is connected in series to the GND connection of DUT and CANSCOPE (black table pen);
If the CAN interface of the DUT is non-quarantined, the program-controlled supply voltage + - serially into the DUT power supply GND line. Using the program-controlled power supply to continuously raise the voltage (one minute 0.1V), the program-controlled power supply voltage when the error frame occurs from the Canscope software.
Loss of the ground: Disconnect DUT and CANSCOPE's black table pen (GND), separately, testing whether an error frame in the Canscope software in 1 minute is tested. If there is no error frame, it is tested.
Power loss: Make DUT to lose the power supply, from the Canscope test bus is disturbed, and the DUT can restore communication after the power supply is reinable. If the power is lost, there is less than or equal to 1 error frame, and the DUT can restore the communication after the power is reinable.
CAN line interrupt: After using Canscope-STESSZ, if Figure 2 is tested for 1 minute, CAN_L is disconnected for 1 minute, can CANH and CAN_L for 1 minute, if the DUT can be restored, the communication can be recovered. pass.
Figure 2 CAN line interrupt test diagram
The CAN line is short-connected to the ground: connect the Canscope-Stressz GND interface with the VDIS-connection. Test CAN_H for 1 minute, CAN_L is shorted for 1 minute, and CANH and CAN_L simultaneously short circuit at the same time, and after recovery, DUT can restore communication, the test passes.
Figure 3 CAN line pair short circuit test chart
The CAN line is short-connected to the power cord: connect the VDIS + of Canscope-Stressz to the DUT power supply. After starting with Canscope-STESSZ, CAN_H is short to the power supply for 1 minute, and CAN_L is shorted for 1 minute, and the CANH and CAN_L simultaneously shorts the power supply for 1 minute. If it is restored, the DTU can restore communication, then the test passes. As shown in Figure 4 (pay attention to the voltage exceeding 24V)
Figure 4 CAN line to the power short circuit test chart
CAN_H and CAN_L short: After using Canscope-STESSZ to start, set RHL to 0, ie, is equal to CANH and CAN_L short circuit, 1 minute, if restored, DUT can recover communication, then test. As shown in Figure 5:
Figure 5 CAN_H, CAN_L short pick test diagram
Test assessment
According to the seven physical error type tests performed by the test process, if the communication can be restored, the fault tolerance performance test in the consistency test of the CAN bus system can be recovered.
CANDT consistency test system
In order to help users avoid errors of manual measurement statistics, improve the accuracy of the test, while reducing the waste of test time, saving labor costs. ZLG Zhiyuan Electronics released a CANDT consistency test system dedicated to the CAN bus, which automatically completes the CAN node physical layer, link layer, and application layer consistency test. It is the only way to be perfect in the current CAN bus test. Physical layer automation test and export the instrument equipment of the report.
Users only need to check the test items in the test page, you can perform one-button automation test, complete data content such as test results, data, wave screenshots, and engineers quickly determine the CAN bus quality of the measured device.
The CANDT consistency test system is based on the necessary equipment such as CANSCOPE, integrated oscilloscope, power supply, etc., can cover the host factory CAN consistency test standard, which establishes a CAN bus test and security system for the host factory and components enterprises.
Any doubts can add ZLG official customer service micro signal consultation: ZLGMCU-888.
Zhiyuan Electronic Introduction
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Article Source: [Micro Signal: Zlg_zhiyuan, WeChat Public Number: Nordic Semiconductor] Welcome to add attention! Please indicate the source of the article.
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