ELM327

macgyver · Joined: 24 Aug 2005 Posts: 12

Is there or does anyone have a driver for the ELM327?

Thanks.

temtronic · Posted: Sun Mar 13, 2011 2:18 pm

If this ELM327 is the Elm elctronics RS232 to OBD-II converter no 'driver' is required. Simple command/instruction structure, similar to controlling modems (AT cmd set).

Humberto · Posted: Mon Mar 14, 2011 8:02 am

macgyver · Joined: 24 Aug 2005 Posts: 12

Maybe i should of said interface software instead of driver. for example if you want to read RPM it would be RPM=(function call)
and return the number not sure how to decipher the at command returns.(converting hex)

Thanks.

temtronic · Posted: Wed Mar 16, 2011 8:23 am

OK, now we know it is the ELM electronics chip, it gets easier.
Depending on the vehicle, some OBD-II commands are valid, others not. So you'll need to know what's available to you.
There is a 'core' of common

One way would be to query every command and see what comes back, if anything.However it could be easier to Google 'your car..OBD-II commands' and see what hits you get.

There are several good references to 'decoding' the results from various OBD-II queries, entire webpages in fact. Let Google be your friend.
As far as converting a hex result to decimal, use the CCS printf function, it'll save a lot of head scratching and time.
How to convert and display the information depends on the 'screen'. Is it going to a PC, local LCD screen( 2by16, 4by20),maybe a GLCD ?

macgyver · Joined: 24 Aug 2005 Posts: 12

For now it will be just back to hyper terminal, but after it will do stuff based on the RPM.

Humberto · Posted: Wed Mar 16, 2011 10:02 am

Well, this is not a trivial task. At first you will need the hardware interface compatible with your car. There are many ODB2 standard
protocols, some of them sharing the same hardware. Most of them use the standards normative defined by ISO or SAE.
For example if you want to communicate with a Ford, they use -mainly- the SAE J1850 protocol, which use PWM coding to comunicate
with its ECU's.
Assuming that you already have the interface, using the ELM327 you can comunicate with the ECU using 'AT' commands.

Regarding how to interact with individual OBD commands, you will find it in:
http://www.elmelectronics.com/DSheets/ELM327QS.pdf

Humberto

temtronic · Posted: Wed Mar 16, 2011 10:42 am

Actually it is trivial...but then all things are relative to what you are familiar with.

Simple serial communications,send a command... receive some data in return..process as required.

All the hard stuff is done in the ELM327, a 'swiss army knife' for OBD-II.
I've hard the Ford only version for years, setup my 25 year old laptop as the 'command and display' unit.

Today,in less than an hour(kinda raining here,so I'm surfing), I found several complete programs written in Basic and C,various references of cars vs. commands, as well as mfr/vehicle specific commands. The Web is a great tool,years ago it took me the better part of a week to find the information.