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On-board diagnostics for CAN

ELM Electronics (Canada) updated its ELM329 CAN interpreter, which allows translating of data from an ISO 15765-4 interface (on-board diagnostics for CAN) into information usable by computers, smart phones etc. available on the EIA-232 port. The device may be applied as a diagnostic trouble code (DTC) reader and reset device, as an automotive test tool or as a teaching aid.

THE CURRENT FIRMWARE (VERSION 2.0) OF THE DEVICE adds several features. A CAN monitor provides automatic switching to and from low-power mode. The EIA-232 transmit buffer was enlarged. Many settings are retained when going from low-power to normal modes. Some timing and setting 'tweaks' to help with problem ECUs were added. Code changes for faster message processing (for busy networks) were made. The device supports ISO 15765, SAE J1939 as well as five user-controllable protocols. It supports CAN periodic (wake-up) messages. Single wire CAN transceiver control is provided. General purpose inputs and an output are available. Arbitrary CAN messages may be sent at any time. The interpreter with an active LED offers software and pin compatibility with the company's ELM327.
To send and receive data an available terminal program (e.g. HyperTerminal, Zterm) may be used allowing to type the characters directly from a keyboard. Several parameters within the interpreter (e.g. timeout value, header (ID) bytes) may be adjusted via AT commands in order to modify device's behavior. A detailed description of the AT commands is given in the data sheet. If the bytes sent to the interpreter do not begin with “AT”, they are assumed to be OBD (on-board diagnostics) commands for the vehicle. The standards require that each OBD command or request has to adhere to a specified format. The valid hexadecimal digits are then combined into data bytes for transmitting to the vehicle. Commands to the vehicle are send embedded into a CAN data frame. The user does not require to consider the used CAN-ID, but has a possibility to change it. After sending the command, the device listens for replies. If a message address (CAN-ID) matches, the received bytes will be converted to ASCII characters and send via the EIA-232 port.
The ELM329 data sheet is also available in the Apple's iBook format, so that it can be used e.g. on an iPad.

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ELM Electronics