So you have a car. And you are a geek. You know kind of I don't really know or care how cars work. And then you got graph like this from your car:
If you take a look at OBD2, you might think that it's only useful to your car mechanic. But, as you can clearly see above, any technology which can draw graphs and uses computers is interesting to me.
You can take two different paths to getting sensor data from your car using open source software. Freediag is project which support dumb (basically level converters between your car OBD2 connector and RS232 or USB) cables. This approach requires very funky boud rates on serial port and lot of knowledge inside software, but offers future-prof route because you can hack software.
So I decided to buy one of those cables (available locally in Zagreb) and ended up with VW cable which did dump some data, but freediag didn't really helped in decoding them.
So, in next step, I opted for one of ELM327 based devices (which decode car protocol within microcontroller) and moved to OBD GPS Logger for data collection. This did work, and result is graph included in this post. In the process, I figured out why you can disconnect both cables (to car and to usb) from micro-controller in metal box: it's the only way to reset it, sigh!
However, now I have a few observations about state of free software for OBD2: I wasn't able to found any software which would introspect all my sensors and log them. This is quite strange since you can inquire car about supported sensors, so that will probably be next thing for me to do. If you have more information, please let me know.