Vehicle Data Bus (CANbus)

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http://www.picoauto.com/automotivetopics/canbus.html

How to connect the oscilloscope
Example waveform and notes
Technical information




How to connect the oscilloscope when dual-trace testing :-
CAN High and CAN Low

Plug one BNC Test Lead onto Channel A of the oscilloscope and the other BNC Test Lead onto Channel B. Connect a crocodile clip onto each of the black (Ground) moulded connectors on the BNC Test Leads, and attach them both to the Vehicle Battery -Ve terminal or a good ground point on the chassis. Attach one of the test probes to each of the red moulded connectors on the BNC Test Leads. Using the Vehicle Tech Manual, identify the CAN-H and CAN-L pins at an accessible point on the CAN network. (Usually available at the multi-way connector at each ECU on the network.) Carefully probe the back of the multi-way connector, using Ch A for CAN-H and Ch B for CAN-L. Alternatively, use the Manufacturers Break Out Box.Pressing the spacebar on the PC will enable live data to be viewed. Vehicle ignition may need to be switched on. The CAN-H and CAN-L waveforms will now appear on the screen, as shown below:

Example VDB (CAN-H & CAN-L) Waveforms

VDB (CAN-H & CAN-L) Waveform notes

In this display, we can verify that data is being continuously exchanged along the CANbus, and it is possible to check that the pk to pk voltage levels are correct, and that a signal is present on both CAN lines. CAN uses a differential signal, and the signal on one line should be a coincident mirror image of the data on the other line. The usual reason for examining the CAN signals is where a CAN fault has been indicated by OBD, or to check the CAN connection to a suspected faulty CAN node. (ECU) The Vehicle Manufacturers manual should be referred to for precise waveform parameters.

The following CAN data is captured on a much faster timebase and allows the individual state changes to be viewed. This enables the mirror image nature of the signals, and the coincidence of the edges to be verified.
Typical CAN-H and CAN-L waveforms in detail

 

 

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 コメント(3)

  

顔アイコン

手持ちのI/Fに使えるFREE SOFTがまだ見つかってない。
じっくりサーチする機会がないので、気長に見つけることにしよう。

2010/3/9(火) 午後 1:42ogw*og*3 ]

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CAN 診断・テスト » CAN/LIN アナライザ >X-Analyser 機能

CAN 診断・テスト » CAN/LIN アナライザ >X-Analyser 機能 http://www.gailogic.co.jp/product/can/spec.html X-Analyser 機能 Echo Server 受信メッセージを自動的にエコーします。この機能で送受信パケットを比較することで、開発者はデバイスの送受信機能が正しいかを確認することができます。 CAN Calculator CAN Calculator は、X-Analyser...

2010/3/10(水) 午前 0:34 [ CQF ]

  
CAN:CAN232:CAN>USB:First step was to hook up a scope to ...

The Hybrid 2004 Toyota Prius - My CAN Project が以下に紹介されて久しい。 http://www.vassfamily.net/ToyotaPrius/CAN/cindex.html それは以下のように展開している。 http://autos.groups.yahoo.com/group/Prius_Miniscanner_MarkIII/ Electrical Isolation 電気的遮断(今回の用語としては電気

2010/3/10(水) 午前 6:30 [ CQF ]

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