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.
OBD InterpretersELM320 - OBD (PWM) to RS232 InterpreterOBD Software Development
ELM322 - OBD (VPW) to RS232 Interpreter
ELM323 - OBD (ISO) to RS232 Interpreter
ELM327
- version history
- OBD to RS232 Interpreter - version 1.3a
- OBD to RS232 Interpreter - version 1.4b
- OBD to RS232 Interpreter - version 2.0
ELM328 - OBD Device Identifier Test IC
Note that we have included a couple of non-OBD protocols that we are often asked about.
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
ELM320 v2.0
data sheet
(74K)
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
ELM322 v2.0
data sheet
(86K)
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
ELM323 v2.0
data sheet
(92K)
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
ELM325 v1.0
data sheet
(179K)
ELM325 v1.0
iBook
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.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).
There are also info files that show which commands apply to which version:
ELM327
AT Commands
(45K)
ELM327
Programmable
Parameters
(36K)
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 and software).
ELM327P v1.3a (PDIP): $19.00 ELM327SM v1.3a (SOIC): $19.00
ELM327 v1.3a
data sheet
(261K)
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 applications where it is preferred to keep the ELM327 connected to the vehicle (fleet applications, etc.). There are also many improvements for protocol support which advanced users may find useful (control of the CAN silent mode, 4800 baud ISO/KWP, etc.).
ELM327P (28-pin PDIP): $23.50 ELM327SM (28-pin SOIC): $23.50
ELM327 v1.4b
data sheet
(373K)
ELM327 v1.4b
iBook
The new ELM327 builds on the v1.4b with a new Activity Monitor, several Low Power improvements, many new Programmable Parameters, new AT commands, and a larger RS232 transmit buffer, to name only a few. If you are considering buying the v1.4b, then you will like the new v2.0 IC better. We expect the new IC to be on sale by mid-June. Pricing will be the same as for the v1.4b:
ELM327P (28-pin PDIP): $23.50 ELM327SM (28-pin SOIC): $23.50
ELM327 v2.0
data sheet
coming soon
ELM327 v2.0
iBook
coming soon
Please note: There is no ELM327 v1.4a, or v1.5, or v1.5a ! Some clone makers have introduced what they call a 'v1.4a', or
a 'v1.5', or a 'v1.5a' but Elm Electronics has never made one.
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. The ELM329:
In addition, we've improved code speed significantly over the v1.0 chip, increased the size of the RS232 transmit buffer, and maintained very good software and pin compatibility with the ELM327. Download a data sheet to find out more.
- 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
- Has an expanded and more friendly CRA function
- Provides an active LED
ELM329P v2.0 (PDIP): $21.00 ELM329SM v2.0 (SOIC): $21.00
ELM329
data sheet
(353K)
iBook
version
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
ELM328
data sheet
(14K)
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