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Application Programming Interface

Communication with control units

With PCAN-ISO TP, PCAN-UDS, and PCAN-OBD-2, Peak System has published APIs for standardized protocols from the automotive sector. The APIs use CAN, are designed for use under Windows, and built on each other.

The programming interfaces use PCAN-Basic to access CAN hardware (Photo: Peak System)

THE THREE APPLICATION PROGRAMMING INTERFACES’ (API) common basis is the PCAN-Basic API for accessing Peak System's CAN hardware in the computer. The PCAN-ISO-TP API is used to transmit data packets according to the ISO-TP standard ISO 15765-2. The programming interface allows transmitting and receiving bigger data packets than the 8 bytes of the CAN network. The transmission of packets up to a size of 4095 bytes per CAN message is possible. The data bytes are transmitted segmented with multiple CAN frames.

Via the PCAN-UDS API, communication with control units takes place according to the UDS standard ISO 14229-1. UDS stands for Unified Diagnostic Services and defines the communication with control units (ECUs). The Windows software tests the controller using various services. The process is done on the client-server principle, where the program is in the position of the client (also called tester). UDS uses the ISO-TP standard as transport protocol, thus UDS can transmit data blocks of up to 4095 bytes size. Besides the exchange of maintenance information, for example, the transfer of firmware is possible.

With the PCAN-OBD-2 API, vehicle diagnostics are performed using OBD-II (ISO 15765-4). For on-board diagnostics, the OBD-II standard defines the exchange of specific vehicle parameters. The client makes a request on the connected control units in the vehicle to which one or several ECUs are answering. As part of OBD-II, the ISO 15765-4 standard describes CAN as a transmission option. This standard defines the exchange of specific vehicle parameters via UDS. All three APIs are available free of charge and can be downloaded from the German company’s website.

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