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Old 06-23-2008, 12:53 PM   #10 (permalink)
OBDuino coder
Magister's Avatar
Join Date: Jun 2008
Location: Montréal, QC
Posts: 212

Titine - '13 Hyundai Sonata Hybrid
Thanks: 3
Thanked 10 Times in 8 Posts
I ordered:

- a Freeduino serial V2.0 + LCD display at NKC ($17+$10)
- an OBD plug at ($5)
- a sample MCZ33290EF from Freescale ($0)

I should be in business, I will find a 510 ohms resistor somewhere here and some push buttons, it's the only component needed.

I even started to write some codes, I started with standard C but why re-invent the wheel to support digital I/O and all, it's in the Wiring/IDE already. So I went back to the standard IDE, and it will be easier to share with other people.

It compiles, obviously it's not tested, copy/paste in IDE

EDIT July 3rd: Maybe I will not update this post anymore, for all information go to the homepage of the project at

Source is available here:

To keep compatibility with already existing cable, the OBD-II to DB9F cable is wired like this:

1---------------5 (Signal ground)
2---------------4 (Chassis ground)
4---------------7 (ISO K line)
6---------------10 (J1850 bus-, future use)
7---------------2  (J1850 bus+, future use)
9---------------16 (Battery)
Do not plug it into a PC!!! This goes to an interface only!!!

You can make it yourself with an OBD-II plug available at for $5+$3sh.
Use at least AWG24 wires especially for Battery and Chassis ground.

Or buy an already made cable at for $10+$5sh

The cable goes into an interface to adapt the ISO signal for the Arduino input.
It concists of a small IC, a resistor, a DB9M that will be plugged with the cable mentionned above, and a few wires that connect to the Arduino board.
Schematic is like this:

Arduino pin 3 -------------5|TX  ISO|4-----------------+------- DB9M pin 4 (ISO K Line)
                            |       |                  |
Arduino pin 2 -------------6|RX  GND|3--DB9M pin 1     / between MC pin 4 and pin 1
                            |       |                  \ goes a 510 ohms resistor
Arduino 5V pin output -----7|VDD  NC|2--               /
                            |       |                  |
Arduino 5V pin output -----8|CEN VBB|1-----------------+------- DB9M pin 9 (12V Battery)
The Arduino is powered by the 12V line coming from the cable too
Arduino 12V input ------------------ DB9M pin 9 (12V Battery)
Arduino GND input ------------------ DB9M pin 2 (Chassis Ground)
2013 Hyundai Sonata Hybrid

Last edited by Magister; 07-04-2008 at 03:02 PM..
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