Friday, January 8, 2010

The CAN Bus and loom developments

I spent most of my time off over the break working on still identifying the remaining plugs on the RX8 loom. I've got it to about 90% now and will have a few extra components delivered soon such as the Fuel Pump/Sender, ABS unit/computer, RX8 Instrument Cluster and a few switches for the dash. Unfortunately I need the computer from the dash to interperet the fuel level signal and possibly to also get the trip computer information. I should be able to make it a bit smaller than it is in this picture.

I also spent some time removing the non-standard things I found in the loom such as parts of an alarm. Whats really confusing though is it looks like some of the wiring going into one of the boxes picture below was coming directly out of the ignition switch plug and appears to be standard wiring but the connectors going into the same box on the other side are spliced into the loom with connectors one might find at a local electronics store...

Because I've identified most of the plugs on the loom I thought it was about time to buy myself a cheap battery and get some power to the loom and see if it works. I did find some damaged wires in the engine loom which were pretty easy to fix. But it seems that one of the horns and ABS sensors were too badly damaged and cut out of the loom before I got it :-( I was able to work out what the wires were at least.

One of the other things I did over the break was develop a program to listen to CAN bus messages on a car equipped with a OBD II port that speaks CAN bus. I was lucky enough to borrow a friends Mazda 2 for this. The program I developed allows me to filter messages, translate the bits of the messages into a number of data types and also perform a formula on this value to get a real world figure such as RPM, Speed etc. All of this can be done while receiving CAN messages and the data can be exported to be viewed later.

Currently the program works with the OBDLink tool I bought recently which translates the CAN headers for me. However the program was initially develop to read unproccessed CAN messages so in theory the application should work with any CAN receiver on a COM port with minor changes. If anyone is interested in a copy then let me know, I will try to find a way to put it up in blogger over the next few days. Here is a screen shot of the app...


  1. Do you have a copy or some source code for the program you've written? I'm also working on a CAN dash display. Thanks, Christian
    hubbellc (at) gmail (dot) com

  2. Hi Christian,

    I will make a post this week with some of the code for the CAN Reader application I wrote.