ELM329
CAN Interpreter
Description
Since 1996, most vehicles have been required
to monitor their own emissions performance and to
report on it through an On-Board Diagnostics (OBD)
port. Initially, several different protocols were used
for the transfer of OBD data, but since the 2008
model year (in North America), only one protocol has
been allowed - the ISO 15765-4 CAN standard.
The ELM329 is a device that can translate the
data from an ISO 15765-4 interface into a form that
may be readily used by computers, smart phones, or
other devices. In addition, the ELM329 provides
support for several other CAN protocols (including
the SAE J1939 truck and bus standard), and for
sending periodic messages, mixed ID messages,
and for monitoring the CAN bus, to name only a few.
The following pages discuss the ELM329’s
features in detail, how to use it and configure it, as
well as providing some background information on
the protocols that are supported. There are also
schematic diagrams, and circuit construction tips.
Features
• Power Control with standby mode
• High speed RS232 interface
• Automatically searches for protocols
• Fully configurable with AT commands
• Pin compatible with the ELM327
• Low power CMOS design
Connection Diagram
PDIP and SOIC
(top view)
MCLR
Vmeasure
Active LED
Control
Memory
Baud Rate
LFmode
V
SS
XT1
XT2
CAN Monitor
In1
In2
PwrCtrl
OBD Tx LED
OBD Rx LED
RS232 Tx LED
RS232 Rx LED
CAN Rx
CAN Tx
M0
M1
V
DD
V
SS
RS232 Rx
RS232 Tx
PwrCtrl / Busy
IgnMon / RTS
Applications
• Diagnostic trouble code readers
• Automotive scan tools
• Teaching aids
Block Diagram
Baud Rate
LFmode
RS232Rx
RS232Tx
18
17
6
7
4.00 MHz
MCLR
1
9
10
RS232
Interface
PwrCtrl / Busy
IgnMon / RTS
PwrCtrl
CAN Monitor
/ A LED
16
15
14
Power
Control
Command
and
Protocol
Interpreter
CAN Module
ISO 15765-4, SAE J1939
ISO 11898
24
23
CAN Rx
CAN Tx
M0
M1
22
V
measure
2
21
Control
Module
CAN
Monitor
5
12
13
In1
In2
Control
11
4
3
25
26
27
28
Memory
status LEDs
ELM329DSB
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