ELM323_09 Datasheet, PDF (1/19 Pages) ELM Electronics – OBD (ISO) to RS232 Interpreter

ELM323
OBD (ISO) to RS232 Interpreter
Description
Since the 1996 model year, North American
automobiles have been required to provide an OBD
(On Board Diagnostics) data port for the connection
of test equipment. This port is used to obtain
emissions-related diagnostics information, and in
some cases can also be used to obtain real-time
vehicle operating parameters.
The ELM323 is a 14 pin integrated circuit that,
with only a few external components, is able to
convert between the OBD data format and the
standard RS232 serial data format. This allows
virtually any personal computer or PDA to
communicate with a vehicle using only a standard
serial port and a terminal program. If desired,
hobbyists can even create their own custom ‘scan
tool’ by adding an interface program.
Please note that while this integrated circuit has
undergone significant changes recently, it is still
considered to be an experimenter’s circuit. It does
support a great many of the ISO9141 and ISO14230
(KWP2000) protocol vehicles, but not all of them,
due to the many interpretations of these standards
that are to be found in use.
Applications
• Diagnostic trouble code readers
• Automotive scan tools
• Teaching aids
Features
• Low power CMOS design
• Crystal controlled for accuracy
• ISO 9141-2 and ISO 14230-4 protocols
• Configurable with AT commands
• Standard ASCII character output
• Four high current LED drive outputs
Connection Diagram
PDIP and SOIC
(top view)
VDD 1
XT1 2
XT2 3
LFmode 4
RS232Rx 5
RS232Tx 6
RSRx 7
14 VSS
13 OBDK
12 OBDL
11 OBDIn
10 OBDTx
9 OBDRx
8 RSTx
Block Diagram
LFmode 4
RS232Rx 5
RS232Tx 6
RS232
Interface
3.58 MHz
XT1 ²
3 _XT2
Timing and
Control
Interpreter
OBD
Interface
13 OBDK
12 OBDL
11 OBDIn
RSRx 7
RSTx 8
10 OBDTx
9 OBDRx
ELM323DSD
Elm Electronics – Circuits for the Hobbyist
< http://www.elmelectronics.com/ >
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