Description

Since the 1996 model year, North American automobiles have been required to provide an OBD, or On Board Diagnostics, port for the connection of test equipment. Data is transferred serially between the vehicle and the external equipment using this connection, in a manner specified by the Society of Automotive Engineers (SAE) standards. In addition to operating at different voltage levels, these ports also use a data format that is not compatible with the standard used for personal computers.

The ELM322 is an 8 pin integrated circuit that is able to change the data rate and reformat the OBD signals into easily recognized ASCII characters. This allows virtually any personal computer to communicate with an OBD equipped vehicle using only a standard serial port and a terminal program. By also enhancing it with an interface program, hobbyists can create their own custom scan tool.

This integrated circuit was designed to provide a cost-effective way for experimenters to work with an OBD system, so a few features such as RS232 handshaking, variable baud rates, etc., have not been implemented. In addition, this device is only able to communicate using the 10.4KHz J1850 VPW protocol that is commonly used in General Motors and some Daimler Chrysler vehicles.

Features

• Low power CMOS design

• High current drive outputs

• Crystal controlled for accuracy

• Fully configurable using AT commands

• Standard ASCII character output

• High speed RS232 communications

• 10.4 KHz J1850 VPW protocol

Applications

• Diagnostic trouble code readers

• Automotive scan tools