Tinkering with ODB II and the CAN bus

[Debrah] is taking his next project out to the garage. He built his own CAN bus reader using a dsPIC.

The nice thing about working with Control Area Network is that it’s a universal standard found on every modern production line automobile. And because of this, the chip you need in order to communicate using that protocol will cost just over a dollar. [Debraj] chose the MCP2551, which comes in several different 8-pin packages. There is even an application note tailored for use with the dsPIC33F family.

The project is running on both 5V and 3.3V rails. This complicates things just a bit, but a level converter makes sure that there’s no communications problems between the chips. A four line character LCD acts as the output during the tests (you can see this in the clip after the break) but he’s already got a second version which looks quite a bit better on the dashboard.

What else can be done with this hack? Well, we’ve seen a method used to read control buttons from the steering wheel before. It all depends on what data your vehicle is transmitting and one way to find that out is to build some hardware and start logging the packets. [Read more...]

CAN sniffing for steering wheel button presses

You can make those buttons on your steering wheel much more functional if you have a way of monitoring them. Don’t even think of cracking open the factory finish to get to the solder points, just tap into the CAN bus and monitor the data traffic.

The small board seen above is the result of a project [Peter Shabino] calls the CAN sniffer. The connector on the left will plug into the Control Area Network system on your car, giving the chips on board something to do. There’s an MCP2551 CAN transceiver (hidden under that linear regulator) and an SPI controlled MCP2515 CAN controller which take care of the particulars of the CAN protocol. The big chip in the middle is a PIC 16F876, responsible for making sense out of the data. From there a MAX232 chip is used to provide a serial interface to connect the device to a computer.

This really isn’t tied down to one particular function. Once you have access to the bus for a microcontroller you’ll only be limited by your firmware writing skills. [Peter] has posted an archive with all of the open source files, as well as an illustrated step-by-step board assembly. We’ve embedded the schematic from that archive after the break. [Read more...]

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