C, bit serial data interface, signal. When the DSC is encoded, the encoding data for the steering column switch with the history memory for fault entries) stores various bits of information that.

April 23, 2013 a complete guide to hacking your vehicle bus on the cheap & easy – part 2 (interpreting the data) in, i covered the basics for how to interface with a vehicle bus using an inexpensive USB or Bluetooth ELM327-based scan tool. In part 2 below, i’ll go over how to actually use that hardware interface to collect and analyze data with the intention of discovering how to interact with the vehicle in some specific way. For my own first project, i wanted to know how to intercept the steering wheel radio remote-control button press events. I replaced my factory radio with a Motorola Xoom 10″ Android tablet in order to have a bigger and better GPS (and OBDII app, and better entertainment options, etc). However, touching the screen precisely while driving can be difficult (especially when bouncing around off-road). Hence why i wanted the factory steering wheel buttons to still control volume, track, play/pause, etc. I’ll use this goal as an example to walk through navigating the bus data.

Source code for the above Android app is available on my GitHub: what you’ll need • patience! • a working vehicle bus hardware interface (the scan tool, see ) • laptop or tablet with serial terminal application capable of logging to a file • (or, a spreadsheet,, etc.) task 1: get a baseline the first task is to gather some baseline data – i.e.

What msgs are flying around the bus when your are NOT doing whatever particular interaction you are looking to find the msg for. I tested and found that with the vehicle not running, i could still use the steering wheel buttons to control the radio. That made things a little simpler since i would be able to gather all my sample data with the engine off and the key in “run” (there are way less msgs on the bus when the vehicle is not running). • issue the following commands (one at a time): ATL1, ATH1, ATS1, ATAL • be sure your serial terminal app is set to log to a text file. • issue ATMA to have the scan tool start reporting all of the bus msgs it sees.

• just press enter after a minute to stop the stream of data. Task 2: log data from the event/interaction in question the next task is to log the bus msgs when the action you are looking for occurs. This could be when something like when the radio changes tracks, when you press the sunroof close button, etc. I wanted to know the msg for each steering wheel button. I did a data collection run for each of the 6 buttons separately.

For each run, i would press the same button 5 times, trying to space the presses evenly about 1 second apart. I wanted to create some sort of pattern that would hopefully stand out in the data stream. • repeat the steps from the previous task, while causing the event in question (or allowing it to happen if you have no control over it). Task 3: analyze the data now you’re ready to analyze the data you collected in order to find just the bus msgs you care about. I used Excel, but you could go with any spreadsheet or database tool that you’re familiar with.

The complete MS Excel spreadsheet for all the examples below can be downloaded here: • paste the data from each of your baseline/test runs into separate sheets of the spreadsheet. All the bus msgs should be in the first column. Add a column header called “ msg“.