What is the relationship between CAN interface and OBD interface?


/ From:Fiberall Technology Limited / Review:114

Through the development of automotive CAN bus, we can get a lot of functions that are not provided by the factory. What is the relationship between CAN and OBD? How can we receive the CAN bus data in the car through the OBD interface?

Car is a closed system, the CAN bus is inside the car, so some people may ask, is it necessary to dis-assembly the car if we want to receive the car's CAN data? Of course no. Now automotive manufacturer has reserved a special position, like a small window, for automobile maintenance, development and other operations, the small window is the car's OBD interface, the connection between car's internal CAN bus and the external equipment will achieve via the OBD interface, it is the only channel which can receive car's CAN bus data without disassembling, with the OBD interface, user only needs to get an OBD diagnostic tool, trouble code reader or a dual-channel USBCAN analyzer. By connecting with the host computer software, the automobile CAN bus data can be viewed and parsed in real time or saved locally.

In fact, automobile manufacturers equip their vehicles with OBD interfaces for two original purposes, one is to detect the car, through special testing equipment like auto diagnostic tool or fault code reader to read the data of the car computer and analyze the car's state and failure; the other is to use it as a vehicle emission standard testing interface, because the OBD diagnostic interface can output a series of sensor data of engine, and oxygen sensors in these data, can also be used to analyze the combustion effect of the engine. Maintenance plants generally use OBD interface to check the fault of the vehicle.

On the other hand, we can analyze the backing signal, brake signal, multi-function steering wheel signal and so on through the CAN bus data received by the OBD diagnostic tool, and then use the analytic signal to design, and finally develop our own unique automobile function. For example, the automobile fault code reader is also developed based on this principle.

The main reason why OBD interface of auto can be used to receive all kinds of automobile data is that the data in automobile is transmitted through CAN bus, and OBD interface is the only interface that can receive automobile CAN bus data without destroying the structure of automobile. So we develop Bluetooth diagnosis module, first of all, we start with OBD interface. The automotive formal state data can be displayed on the mobile phone, in fact, it is the process of automotive CAN bus data parsing, and OBD decoding development module can completely replace this step, do not need to learn to parse their own CAN bus data, only need to design a Bluetooth chip, can parse the CAN bus data sent to the mobile phone and then the phone APP can receive the information.

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