Our "OBD Interpreter" ICs are designed for use with vehicles that use one of the standard OBDII
(On Board Diagnostics) protocols. Refer to the help > obd section to
see if your car uses one of these protocols.
ELM320 - OBD (PWM) to RS232 Interpreter
OBD Software Development
ELM322 - OBD (VPW) to RS232 Interpreter
ELM323 - OBD (ISO) to RS232 Interpreter
ELM325 - J1708 Interpreter
- version history
- OBD to RS232 Interpreter - version 1.3a
- OBD to RS232 Interpreter - version 1.4b
- OBD to RS232 Interpreter - version 2.0
ELM329 - CAN Interpreter
ELM328 - OBD Device Identifier Test IC
Our OBD integrated circuits support a variety of protocols, but no one chip can support all of
the protocols that are currently in use. To help you choose, we have put together the following
Note that we have included a couple of non-OBD protocols that we are often asked about.
ELM320 - OBD (PWM) to RS232 Interpreter (v2.0)
ELM322 - OBD (VPW) to RS232 Interpreter (v2.0)
The ELM320 allows you to talk to your 41.6KHz J1850 PWM protocol vehicle through a standard RS232
serial connection, using only simple ASCII commands. This data protocol was commonly used in many
Ford Motor Company vehicles (but is now being replaced by CAN).
The data sheet shows how to connect this IC into a low cost circuit which provides all the functionality
of a scan tool that cost considerably more. Once built, a simple terminal application, and perhaps a
USB to RS232 converter are all that are needed to 'talk' to your vehicle. You need only send a few
simple keyboard commands (ascii characters) and all the data formatting, error checking, bus
arbitration, etc. is then handled by the ELM320 for you.
If you presently use one of our v1.x ICs, you will be pleased to know that this version (v2.0) is
pin-compatible with your IC (the only difference is that linefeeds are now on by default). If your
IC is mounted in a socket, you can simply unplug the old IC and plug in the new.
ELM320P (8 pin PDIP): $14.50
ELM320SM (8 pin SOIC): $14.50
ELM323 - OBD (ISO) to RS232 Interpreter (v2.0)
Similar to the ELM320, the ELM322 is for connecting to an OBDII equipped vehicle which uses the
10.4KHz J1850 VPW format. This standard is typically used in General Motors Corporation and some
(Daimler) Chrysler vehicles.
As with all of our OBD ICs, the user need only issue the desired commands through an RS232 serial
connection and the data formatting, error checking, bus arbitration, etc. on the vehicle side is
taken care of by the ELM322. This allows experimenters to inexpensively create their own scan tool.
If you presently use one of our v1.x ICs, you will be pleased to know that this version (v2.0)
is pin-compatible with the old, so you can simply replace your IC if you want to upgrade.
ELM322P (8 pin PDIP): $14.50
ELM322SM (8 pin SOIC): $14.50
ELM325 - J1708 Interpreter (v1.0)
The ELM323 completes our trio of single function OBDII ICs. It supports the ISO 9141-2 and
ISO 14230-4 standards that are used by many vehicles throughout the world.
The ELM323 transparently converts between a 10.4KHz ISO data stream and standard ASCII characters,
allowing trouble codes and operating parameters to be easily retrieved without the need
for special software. No knowledge of data formatting, error checking, bus initiation etc.
is needed either, as the ELM323 handles all of it for you.
The present version of the ELM323 (v2.0) provides several programmable features that the
previous versions did not offer. It allows programmable header bytes, adjustable timeouts,
the ability to report in the packed data mode, and offers a special monitoring mode as well.
This is in addition to all of the capabilities that the v1.x ICs offered - the full seven byte
command structure, two line (K and L) initiation, software selectable linefeeds and character
echoing, and the visual feedback provided by the four LED outputs.
If you currently use one of our v1.x ICs, you will be pleased to know that this version (v2.0) is
pin-compatible with the old, so you can simply replace your present IC with one of these, and
immediately begin enjoying these new features.
ELM323P (14 pin PDIP): $15.50
ELM323SM (14 pin SOIC): $15.50
ELM327 OBD to RS232 Interpreters
This is our latest vehicle diagnostics interface chip - this time for heavy duty vehicles that use J1708
with J1587 (or J1922). Although these protocols are being phased out (they're being replaced by
J1939), there are still a very large number of vehicles that use them.
The ELM325 is a very capable product, as you would expect. You can monitor
the data bus, selectively filter what you see, send messages, and retrieve replies, as well as
adjust timing, priorities, output formatting, etc. all through a very easy to use ascii interface.
In use, the ELM325 is almost identical to our popular ELM327, ELM329, etc. products. A simple
terminal program will get you going, and because it's ascii-based, custom interfaces are easy to create.
The ELM325 is a 14 pin CMOS integrated circuit that only requires a handful of components to make
a complete interface tool. The output is serial, as that's the most versatile - there are
solutions available for you to connect to USB, RS232, Bluetooth, ethernet, Wi_Fi, etc. Have a look
at our data sheet for a discussion of a couple of these (see the Example Applications section).
ELM325P (14 pin PDIP): $15.50
ELM325SM (14 pin SOIC): $15.50
Elm Electronics has been producing the ELM327 integrated circuit since 2005. We have updated
the product several times in response to your requests, and as a result have produced many
versions of the IC over the years.
ELM327 - OBD to RS232 Interpreter (v1.3a)
We are often asked just what the differences are between the versions, and so
provide information on our 'obd help' page (http://www.elmelectronics.com/obdtips.html).
We also provide these info files that show which commands apply to which version:
Basically, you will find that the version 1.3a IC is a full-featured device that meets the needs of 99% of all
users. Version 1.4b adds the ability to go to Low Power mode, and a few J1939 refinements, but it has now
been replaced with version 2.0 chip.
ELM327 - OBD to RS232 Interpreter (v1.4b)
This integrated circuit has been the industry standard for many years. It provides support
for all of the mandated OBDII protocols:
in addition to variations on the above, and SAE J1939, etc.
- SAE J1850 PWM
- SAE J1850 VPW
- ISO 9141-2
- ISO 14230-4 (KWP), and
- ISO 15765-4 (CAN)
You will find that it is very
easy to use, and that there's a lot of support for it on the web (both construction ideas
The ELM327 v1.3a has been replaced by the v2.0, but remains available because of customer requests.
327P_V13 (ELM327 v1.3a in 28 pin PDIP): $19.00
327SM_V13 (ELM327 v1.3a in 28 pin SOIC): $19.00
ELM327 - OBD to RS232 Interpreter (v2.0)
The main difference between the v1.3a and v1.4b chips is that the v1.4b offers the ability to go to a
low power 'sleep' type mode. This is great for installations where it is preferred to keep the ELM327
connected to the vehicle (fleet applications, etc.).
There are also several improvements to protocol support which advanced users may find useful
(control of the CAN silent mode, 4800 baud ISO/KWP, etc.).
The ELM327 v1.4b has been replaced by the v2.0, but remains available because of customer requests.
327P_V14 (ELM327 v1.4b in 28 pin PDIP): $23.50
327SM_V14 (ELM327 v1.4b in 28 pin SOIC): $23.50
ELM329 - CAN Interpreter (v2.1)
The new ELM327 is an improved version of the popular v1.4b. It has an Activity Monitor,
several Low Power improvements, many new Programmable Parameters, some new AT commands,
and a larger RS232 transmit buffer, to name only a few of the many changes.
If you were considering buying the v1.4b, then you will like the new v2.0 IC better. Pricing
remains the same as for the v1.4b:
ELM327P (28 pin PDIP): $23.50
ELM327SM (28 pin SOIC): $23.50
Elm Electronics makes integrated circuits only!
You must solder them into a circuit in order to use them.
If you want a 'ready-made' circuit (ie with Bluetooth, USB, WiFi, etc.) then you will have
to search the web for it. We can not guarantee that a particular company will use our products,
so be careful. Some times, you just get your money's worth.
A few clone makers have carefully worded ads that make it seem like they are using genuine
version v1.4a, v1.5, v1.5a, or v2.1 Elm chips. These can not use Elm Electronics ICs as we have
never made those versions.
The ELM329 is our CAN-only device that provides more CAN support than is in our popular
ELM327. The current firmware adds several new features that users have requested.
This latest version improves code speed significantly over the previous chip, and adds new
filtering for what we call 'CAN input frequency matching'.
- Supports ISO 15765, and SAE J1939
- Also provides five user controllable protocols
- Supports CAN periodic (wakeup) messages
- Has a CAN Monitor for automatically switching to low power mode
- Provides single wire CAN transceiver controls
- Has general purpose inputs and an output
- Can send an arbitrary CAN message at any time
- Provides an active LED
The ELM329 maintains very good software and pin compatibility with the ELM327, so you will
find the transition to this IC to be straight forward.
Download a data sheet for all the information.
ELM329P (28 pin PDIP): $21.00
ELM329SM (28 pin SOIC): $21.00
OBD Software Development
ELM328 - OBD Device Identifier Test IC (v1.4)
The ELM328 IC is electrically identical to the ELM327 except that it offers one new AT command
which can be used to reset the @2 Device Identifier lock. This provides code developers with
a means to repeatedly test code which writes to the @2 device identifier, without requiring a
new IC each time.
The ELM328 supports all of the ELM327 v1.4 AT Commands, but it
does not transmit OBD messages - it is for code development only,
and not for use in scan tools.
ELM328P (28 pin PDIP): $28.00
ELM328SM (28 pin SOIC): $28.00
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