Application Notes

Occasionally, we are asked about circuit design or construction, and are not able to provide an adequate explanation with an FAQ. For these cases, we have developed Application Notes that we hope you will find helpful:

AN01 – Transistor Testing

It’s very difficult to know which lead is which for many transistors. Sure, there are special testers, but what if you don’t have one? This Application Note shows one method of identifying the three leads of an NPN or PNP transistor, and it doesn’t require much more than a voltmeter.

pdf iconApp Note 01

AN02 – ELM327 Circuit Construction

This Note provides some helpful advice for those that are building the ELM327 Example Application circuit shown in Figure 9 of the data sheet. It provides a few suggestions, and also shows typical voltages that should be found, both before the main ICs are installed, and afterward.

pdf iconApp Note 02

AN03 – ELM327 Low Voltage Resets

If your ELM327 circuit is experiencing occasional ‘LV RESET’s, then you should read this Note. It talks of the main cause of the resets, and provides two methods to prevent them.

pdf iconApp Note 03

AN04 – ELM327 and Bluetooth

We have had a large number of questions asking about the use of Bluetooth modules with our ELM327. This Application Note discusses some ways in which you might connect them.

pdf iconApp Note 04

AN05 – Bench Testing OBD Interfaces

This note provides some tips on testing your OBD Interfaces before connecting them to a vehicle. It’s a collection of some of the more common issues that we’ve been asked about over the years, with an emphasis on testing the CAN protocols. If you are building your own circuits, you will likley find this note to be helpful.

pdf iconApp Note 05

AN06 – ELM327L and the PL-2303HX

Been wondering if you might be able to use one of those inexpensive PL-2303HX cables with your next ELM327L project? Maybe with another project? Well the information is pretty thin on just how to use them, so we created this application note. It’s likely just what you need.

pdf iconApp Note 06

AN07 – Sending Arbitrary CAN Messages

We are often asked about how to send arbitrary CAN messages. Typically the user wants to send data bytes of their own choosing and does not want extra (PCI) bytes inserted or removed for them. This application note shows how to send CAN messages of your own choosing, with our ELM327, ELM327L, ELM329 or ELM329L products (version 1.3 or newer).

pdf iconApp Note 07

… and more will be coming.

If you have comments on any of the above Application Notes, or have an idea for a new Note, we would appreciate hearing from you. Just send an email to: