Embedded software development for a CAN based vehicle diagnostic system

OData support
Szabó Zoltán
Department of Automation and Applied Informatics

Presently all the road vehicles must have a built-in OBD (On-Board Diagnostics) system. Using this system makes the user to be able to monitor the vehicle by reading their sensors, and eases the way of the diagnosing of a faulty vehicle by reading the trouble codes diagnosed by the ECUs (Engine Control Unit). Since 2007 almost all of the published vehicle’s OBD system use the CAN communication protocol. In order to get the information from an OBD system, it is necessary to have a device which can communicate in a CAN bus, and can provide the information to the user in a proper interface. In practice there are two device family which is implement this functionality: the ELM and the STN families.

The objective is to plan an embedded software for a ready embedded hardware, which can communicate in a CAN bus and can read the said diagnostic data, then it can send it to an external unit in another communication channel. With this embedded system the using of the ELM and STN devices will be unnecessary.

This examination paper starts with the OBD system’s introduction, in which the functionality of the system is written in detail, and the OBD’s CAN protocol is introduced. In the next chapter there is a comparison between the ELM327 and the STN1110 devices. The last chapter of the paper contains the documentation of the used software platform and the done embedded software.


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