ELM320

Features:

• Low power CMOS design
• High current drive outputs - up to 25 mA
• Crystal controlled for accuracy
• Configurable with AT commands
• Standard ASCII character output
• High speed RS232 communications
• 41.6KHz J1850 PWM Protocol


Application

• Diagnostic Trouble Code Readers
• Automotive Scan Tools


Specifications

Storage Temperature....................... -65°C to +150°C
Ambient Temperature with
Power Applied....................................-40°C to +85°C
Voltage on VDD with respect to VSS............ 0 to +7.5V
Voltage on any other pin with
respect to VSS...........................  -0.6V to (VDD + 0.6V)

Note:
Stresses beyond those listed here will likely damage the device. These values are given as a design guideline only. The ability to operate to these levels is neither inferred nor recommended.


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 these connections, 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 ELM320 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 ELM320 was designed to provide a cost-effective way for experimenters to work with an OBD system, so many features such as RS232 handshaking, variable baud rates, etc., have not been implemented. In addition, this device is only able to communicate using the 41.6KHz J1850 PWM protocol that is commonly used in Ford Motor Company vehicles.