Modern cars need the right hardware and software for diagnostics. In this thesis, we focus on the Volkswagen KWP1281 protocol, which was widespread in the VAG group of vehicles before the introduction of the standardised CAN protocol. The aim of the thesis was to learn about the operation of the diagnostics and to implement the KWP1281 protocol in software on a dedicated microcomputer. We also added circuitry to convert 12 V signals from the car to 5 V suitable for the UART pins on the microcomputer, and circuitry to power the microcomputer directly from the standardised OBD interface. The microcomputer connects during operation to a VPS web server running on a cloud platform from a commercial service provider. The server runs an application in the Go programming language which serves as a back-end to a simple web interface. The latter allows us to control and manage the microcomputer by means of read and erase operations of the error codes stored in engine control unit and capturing the current diagnostic parameters in real time. Captured diagnostic data is stored in the BoltDB database, allowing later inspection and analysis. Final implementation works well, so our goal of learning about the KWP1281 protocol and creating a working prototype on a dedicated microcomputer was successfully achieved. The final prototype works well as a basic diagnostics tool for vehicles using KWP1281 protocol.
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