ELM328
OBD Device Identifier Test IC
Description
The ELM327 “OBD to RS232 Interpreter” IC
introduced a new feature with v1.3 - the ability for a
user to store a unique 12 character identifier code.
This identifier can be read at any time, but it can not
be changed once it has been set.
Software developers will have difficulty proving
their code with this “write once, read many” feature,
so we have introduced the ELM328 integrated circuit
as a development tool for them.
The ELM328 is a special version of the ELM327
- it is identical electrically, but the firmware has one
new command (AT @0) that resets the @2 identifier
lock.
Connection Diagram
PDIP and SOIC
(top view)
MCLR
Vmeasure
J1850 Volts
J1850 Bus+
Memory
Baud Rate
LFmode
V
SS
XT1
XT2
VPW In
ISO In
PWM In
J1850 Bus-
OBD Tx LED
OBD Rx LED
RS232 Tx LED
RS232 Rx LED
CAN Rx
CAN Tx
ISO L
ISO K
V
DD
V
SS
RS232 Rx
RS232 Tx
PwrCtrl / Busy
IgnMon / RTS
Features
• Based on the latest version of the ELM327
• Allows testing of the @2 and @3 functions
Applications
• ELM327 code development only
(not suitable for OBD scan tools)
Usage Notes
1. The ELM328 electrical connections and characteristics are identical to the ELM327 integrated circuit,
so that it can be directly substituted into an ELM327 circuit.
2. The ID string sent at power up, or in response to AT I is “ELM328 v1.4” and not “ELM327 v1.4”.
3. The ELM328 offers one new AT command - the @0 command, which unlocks the @2 identifier,
restoring it to the factory new condition. ELM327 software developers may repeatedly experiment with
the @2 and @3 commands, using AT @0 to reset the identifier as required.
4. The ability to send OBD commands has been removed from the ELM328. If you try to send an OBD
command, the ELM328 will always act as if no ECU is connected, and no data will be transmitted.
Ordering Information
These integrated circuits are 28 pin devices, available in either a 300 mil wide plastic (‘skinny’) DIP format
or in a 300 mil SOIC surface mount type of package. To order, add the appropriate suffix to the part number:
300 mil 28 pin Plastic DIP.............................ELM328P
300 mil 28 pin SOIC............................ ELM328SM
ELM328DSB
Elm Electronics – Circuits for the Hobbyist
www.elmelectronics.com
1 of 2
ELM [ ELM ELECTRONICS ]
