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
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 4 different types of interfaces ELM 327:
NB: the above 4 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, WiFi
|Application Android||Application iOS*
Despite the appearances these 4 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 2.0 version of its ELM 327 circuit.
Following users requests asking where they could purchase an ELM327 interface we decided to open our own online shop (www.boutiqueobdfacile.com). If you decide to purchase your material through our shop it will give you the following advantages:
Please find below the links to the products that we are selling:
|ELM327 Bluetooth||ELM327 WiFi|
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:
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.
The electronic box has got 3 main components that make it an interface:
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.
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:
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:
|version 1.2 and more||ATKW0||OK|
|version 1.3 and more||ATS0||OK|
|version 1.3b and more||ATFE||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.
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:
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.
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.
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...
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.