Slashdot Mirror
Interacting with Onboard Car Computers?
joshmccormack asks: "I've seen lots of projects where people are making great looking computers that fit into the dashboard of their cars that play MP3s, movies and even some that do some GPS and mapping stuff. I'd love to find projects where computers connect with the on board computers in most cars from the mid 90s on to show temperature and performance of various parts of the car. There are diagnostic tools that mechanics use, and that you can get to get data, but I'm particularly interested in real time, in-dash, open source options."
I don't think any car company release their onboard computer protocols. They could be running RS232 or 10baseT for all we know.
Best chance for you is to wire into the analog sensors that they are using!
Bye!
I bought an OBD2 interface board from scantool.net works pretty well, pretty easy interface protocol.
I wrote up some functions to grab different data from the box, and drop it in a struct for later processing. I also wrote up another function to handle the later processing and give you the raw value. Pretty simple code really.
The only problem I ran into (which was the kicker for me), I was only able to get about 3 samples per second from my Jeep's computer...Hardly fast enough for a realtime display of all the normal dashboard information, but cool none-the less.
Maybe I'll zip up the code I wrote and post it on the net, now that it's getting warmer I might be interested in spending some time on it.
It's been seen on here a few times, but it's currently the best linux-based open-source car computer website. It has OBDII compatibility via a FreeDiag driver. The software has been slow in development, but lately things have been picking up quite nicely.
http://www.dashpc.com has all the juicy details about how to build your own DashboardPC and how to interface with your car via your PC.
Don't think that a small group of dedicated individuals can't change the world. It's the only thing that ever has.
another build it your self ecu would be Megasquirt [http://www.bgsoflex.com/megasquirt.html]. Otherwise, i'd suggest just reading the input from all the sensors, they're pretty easy to interface, just make sure all your circuits are designed properly so you don't burn anything out. +Temperature sensor: resistance changes with temp, higher the resistance, the colder it is (not all are like this). Example, on my Saab, 1000 ohms is about 8 degrees F. +O2 sensor: if you want to know the fuel/air mixture, the output from the O2 sensor normally ranges from 0-4 volts. Figuring out timing and dwell is a bit harder, requiring crankshaft position sensor, and knowing the current rpms of the shaft. Most automotive books for your car will describe the various sensors, and their outputs.