Saturday, May 23, 2009

Great Can Bus hacked page on a Saab

I have found this really interesting page here. It is from a guy who reverse engineered the instrument bus on a Saab. This bus is called I-bus and is based on CAN bus. He gives a lot of information on how he did it, starting from locating the connector, attaching to the bus and interfacing with the PC, along with the tools he used.
It is very similar to what we would like to do and thus we can get lots of advices from it. There are important differences though. He bought ready-to-use CANBUS connectors while we are trying to do it by ourselves. Well actually he says that he tried to do it himself but could not make it work so he switched to commercial products, but he does not give much information on how he tried and what did not work.
The other big difference is that as he is using commercial products, he also has access to programs on Windows platform that can decode bus messages and help during reverse engineering. We won't have these programs because of our do-it-yourself choice and also because we plan to use Linux to get access to the bus by using a serial interface. This is clearly much harder to do but I hope it is not so hard that we will eventually be forced to switch to commercial products.
We will also have to develop our own programs on the Linux platform, but this should not be a big problem. We have to look around for already existing projects to see if we can reuse some code.

This page also gives us a real example of what the message on CANBUS looks like and how they are used by the car. He also explains how the information is spread on multiple messages as for the case of the radio display. Definitely an helpful page!

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