Diagnostic interfaces

Table of content

Introduction of the ELM interfaces
Where to buy an ELM interface?
How to use the ELM 327 interfaces?
How does the ELM 327 interface work?
Tips on the ELM 327 interfaces
ELM circuit for electronic engineer
Other types of interfaces

Introduction of the ELM interfaces

There are several types of interfaces. The most common are found on the chip from ELM Electronics. The ELM 327 is more used and practical as it is compatible with all the OBD systems i.e. KWP, PWM, VPN and CAN. The other circuits are only compatible with one system: the ELM320 is compatible with the PWM; the ELM322 with the VPN and the ELM323 with the KWP.

What type of communication for my interface?

We know 3 different types of interfaces ELM 327:

RS232 (RS or Series): this outlet is less and less used on the new PCs. This is the cheapest option.
USB: slightly more expensive than the RS and requires to install a FTDI driver. Good point: all PCs are equipped with a USB outlet.
Bluetooth: the most expensive one. The good point is that it is wireless.

NB: the above 3 interfaces are compatible with our software.

Please find below pictures of the 3 different interfaces using this integrated circuit (microchip) :

From left to right: USB interface in metal enclosure, USB interface in plastic enclosure, Bluetooth

Despite the appearances these 3 interfaces are similar on an electronic point of view. Only the external aspect and the type of connection are different. The main electronic system is a circuit ELM 327.

The firmware can also change. There are officially 2 different versions of firmware, the 1.2 and the 1.3. Only the very experienced users will be able to tell the difference between a firmware 1.2 and a 1.3 as the basics remain the same. On the internet we can also find the 1.5 version. We bought one ourselves so we can definitely say that it does not exist. It is actually a copy of the 1.2 version called 1.5. You can find in our link tips, how to make sure that the version that you have is the right one.

News :Elm Electronics have just released the 1.4 version of its ELM 327 circuit. View their website for more details. here

Where to buy an ELM interface?

Our official shop :

Following users requests asking where they could purchase an ELM327 interface we decided to open our own online shop (www.boutiqueobdfacile.fr). If you decide to purchase your material through our shop it will give you the following advantages:

With every interface we are including the full version of our software EOBD-Facile.
The interface is in stock, it will be dispatch within 48h maximum by Colissimo International or La Poste Export Suivi.
The interface would have been tested and reparametered.

Please find below the links to the products that we are selling:

ELM327 plastic: www.boutiqueobdfacile.fr/elm327-obd2/10-elm-327-usb-obd2-metal.html
ELM327 metal: www.boutiqueobdfacile.fr/elm327-obd2/11-elm-327-usb-obd2-plastique.html
ELM327 Bluetooth:: www.boutiqueobdfacile.fr/elm327-obd2/12-elm-327-obd2-bluetooth.html

Abroad :

Most of the suppliers are abroad, most of the time they are located in the following countries: China, Hong Kong, USA. Before purchasing anything we advise you to check the following points:

The price includes any customs fees or any VAT (suppliers ex EU). Sometimes a foreign supplier will not include the customs fees. The transport company will then charge you for them at the delivery (around 20% of the value of the goods).
Type of delivery. If you cannot be at home on daytime you should chose a delivery by the post office. Companies such as DHL or FedEx require people to be present at the delivery. If you buy from a company abroad, make sure you are aware of the delivery time (up to 15 days).
Check that in case of malfunction the supplier does replace the product (or gives you your money back).

How to use ELM 327 interfaces?

1. Installation of the drivers:

RS232: No installation required.
USB : To connect the interface to the computer it is necessary to install the FTDI driver (available in the downloading section of our website).
Bluetooth: It is necessary to pair the interface to your computer before use. The code is 1234.

2. First connection to the vehicle:

Connect the interface to the OBD of your vehicle.
Connect the interface to the USB outlet of your computer.
Launch the software EOBD-Facile by clicking twice on the EOBD-Facile.exe icon.
Turn on the engine. The engine LED of the dashboard must be on.
Click on the button « connect ». The software will connect to the vehicle automatically. In case of any problem have a look at the help file of the software aide.pdf.

3. The different types of LED:

Power (LED red): Shows that the interface is powered up. Be careful this indicator is light red when only the USB cable is connected. The interface is correctly powered up only when the indicator is dark red.
Tx OBD (LED yellow): flashes when data are sent from the interface to the vehicle.
Rx OBD (LED green): flashes when data are sent from the vehicle to the interface.
Tx USB (LED yellow): flashes when data are sent from the PC to the interface.
Rx USB (LED green): flashes when data are sent from the interface to the PC.

Tips :On plastic and Bluetooth interface there is no indication on the LED. When it is powered the red LED comes on and quickly after the 1. Tx OBD, 2. Rx OBD, 3. Tx PC, 4. Rx PC.

How does the ELM 327 interface work?

The electronic box has got 3 main components that make it an interface:

Adaptation of electric tension: The car networks have tension levels that need specific drivers. The ELM 327 has various protocols so it requires several drivers. Those protocols can be classified in 3 categories, the networks CAN, the lines K/L and the PWM/VPN.
The chip ELM327: The integrated circuit is the main part of the interface. It selects the protocol and makes it compatible with the modern PCs. This small circuit (pace 4MHz) serves as link between the protocols.
Adaptation of the tensions for the PC: as the electronic chip cannot communicate with a computer it is necessary to adapt the electric levels before sending any information.

After this short introduction the word interface makes more sense. The role of the ELM327 is to link 2 different worlds. In one hand the world of the cars with all its standards (high level of strength and low price) and on the other hand Informatics more focused on modularity.

Tips on the ELM 327 interfaces

How to be sure of the software version?

Sometimes the quality of the interfaces is not there, as we explained above, the version of the software is not always reliable. We can find some versions that are not listed by the supplier (rappel: ELM Electronics). Feedback from users made us aware of the fact that some unofficial versions were available. So, just to make things clear:

Real versions: 1.0 1.1 1.2 1.3 1.3b 1.4
Dummy versions: 1.2a 1.3a 1.4a 1.5 1.5a (and in general all the versions not listed in real versions)

We will not explain why we can find those unofficial versions. The main point is how to check the capacities of an interface. To do so, we advise you to take the following steps:

Connect to your vehicle with our software
Use the « console » window to type the commands described in the following table:
If the interface says « OK » then the order has been recognised, otherwise you will get "?" to let you know that the command has not been recognised
Important : this do not forget to Reset the connection if you want to carry on communicating with you vehicle.

Connectivity	Order	Expected answer
version 1.2 and more	ATKW0	OK
version 1.3 and more	ATS0	OK
version 1.3b and more	ATFE	OK
version 1.4	ATSS	OK

This test will allow you to determine the level of functionality of your interface. Even if it is only a simplified version of the entire process it is efficient and quick. You must know that our software is working 100% with the interfaces from the 1.2 version even if it uses some commands of the 1.3 version.

How to improve the pace of the interface?

Most of the ELM interfaces are made to exchange data with a computer at 38400 baud pace. This pace is an internal parameter of the interface that can be modified. Increasing this pace will increase the reactivity of the interface (from 10 to 20%), which reveals useful when it comes to check on fast variations (i.e. the evolution of the figures of the sensors in the graph mode of our software).

To change the parameters of your interface to make it works at 115200 baud use the following steps:

Connect to your vehicle with our software
Use the « console » window to type the commands described in the following table:
Type: AT PP 0C SV 23
The interface will reply: OK
Type: AT PP 0C ON
The interface will reply: OK
The new parameters will be taken into account after a reboot of the interface (plug/unplug from the vehicle)

Attention: this parameter will then be saved and your interface will work at 115200 baud every time. Make sure that the computer systems that you usually use with your interface can handle this pace.

ELM circuit for the electronic engineer

If your interface ELM has broken down or if you want to create your own circuit the drawing below will be very useful to you. It represents a circuit of an interface ELM 327 type RS232. The basic of the circuit is still the same no matter the connection used (RS232, USB or Bluetooth). The main difference will be the components connected to the pins 17 and 18 of U1 (integrated circuit ELM327).

For the interfaces USB type, a FTDI FT232 component is used to « convert » a RS connection into a USB one as well as the adaptor cables USB <-> RS232. For more information visit the FTDI website http://www.ftdichip.com.

Bluetooth Interfaces are used with a modem RS <-> Bluetooth.

Click on the pictures to enlarge them

In case of breakdown :

ELM Electronics created an application note very well done and useful going through the different levels of tension and a testing process. You can find this document by clicking on the following link: http://www.elmelectronics.com/AppNotes/AppNote02.pdf

If you are not used to DIY, we would like to let you know that we recycle interfaces for personal purposes. You can send it to us and then help us with our project...

Other types of interfaces

Our software is only compatible with the ELM interfaces, but other companies have created interfaces with similar abilities that the ELM circuit.

i.e.: http://www.ozenelektronik.com and their interfaces myOBDics

On the market it is also possible to find some professional product as the ones used by the drivers i.e. Clip, Lexia, etc. Those products remain dear and because of their specificities they can only be used by makers, which is not the case for the ELM.