An Open source , CAN-bus based automotive wiring harness for the masses

[cgriffin]

I have lurked here for quite a while and I know if I have an electronics problem chances are someone on this forum has the answer for it.  I have also noticed that there are an awful lot of automotive based circuits discussed here. 

My idea is a complete multi-microcontroller based wiring harness networked with CAN-bus that could be used for and expanded to everything from the smallest battlebot to the largest RV/motor home,  and hopefully a few hot rods in between.

Its brand new  I'm looking for momentum, general help and folks to bounce ideas off of.

http://www.candy-group.org

[ante]

Hi cgriffin,

Welcome to this forum!

The CAN-bus system (Bosch) is already highly developed especially for vehicles. Can you try to explain where you want to go with it?

[cgriffin]

It is not my intent to develop the CAN-bus network itself but simply use the now integrated CAN-bus ability inherent in some PICs to communicate with a PIC based controller and dictate the functions of the automobile/robot/whatever.

If for instance you wanted tail lights that would blink rapidly during an emergency (very quick and unexpected) stop it would be very difficult to do this with a standard aftermarket or otherwise wiring harness. With the harness I propose you simply need to access the VSS (vehicle speed sensor) output and brake switch. Program the central controller turn the brake light output pin on and off at a faster than normal frequency if VSS changes downward at an unacceptable rate.

Each and every function of the harness software configurable.

[cgriffin]

Also microchip sampled me 15 of those MCP2551 tranceiver units  ;D

I was initially going to use several PICs and have them perform all the functions possible internally and only put on the network what would be absoloutly necessary.  This however proved to be a nightmare to even think about much less program for.

I realized I needed to build around a central controller

I now propose to first program each of the modules sans controller with a really simple CAN bootloader.  When The module is reset it will ask the controller for software, at which point the controller having been preprogrammed with the modules expected purpose sends the module a very simple program that only sets the I/O pins, addresses any input changes to the controller via the network and  listens to the controller to be told what to do. 

The controller is programmed with the actual meat of the software and its purpose is to listen to all inputs from the network and act on them by addressing the proper module and instructing the module as to what it should do with its output pin.


this is how a single interaction would go.


1. left turn signal switch is activated and sets a pin on the cabin module
2. cabin module reports changes the state of the pin to the controller via the network
3. The controller notes this change and addresses the under hood module to turn on and off and a set frequency
4.  blinker operates at said frequency.


This allows the module PICs to be basically dumb and the controller will be the central programming repository.

[ante]

Ok, I see. You like to hack into the existing system to make mods to the different functions. Could be fun but how sensitive are these circuits if you try to override the existing signals and commands? You probably have to go all the way to the “brain” to take control not to make a mess here. I know cases where cellular phones have done “brain damage” to the system and strange things have happened. In some cars the AC runs amok and forces the driver to go to the workshop with the windows down not to freeze to death! ;D

[cgriffin]

I don't intend to use any existing harness out there. This will be a completly new harness and the only throwback to Bosch will be the use of CAN-bus,  specifically using the CANopen stack (opensource CAN-bus).  I wont need to integrate into anyones existing method for addressing the modules or module functions,  I can make my own. 

One of the big reasons I did this is because my 1978 TA almost caught fire because I tried to roll down the electric windows and the switch toasted.  I am not using that vehicle as a test mule as it is perfectly original and is in storage.  I will be using a 1967 firebird 400 that will bristle with high tech hardware.

This is a good time to develop since I just got all the old garbage stripped out and will be sending it out for Alkaline dip soon,  then metal work begins, then drop LS1 motor into it,  pipe in the twin turbos etc. 

I have a good bit of time to at least get a rudamentary system going.

Any thoughts?

[ante]

First of all I like the idea of an LS1 with twin turbos, the drawback is the cost of gas though! :o  Other than that; go for it! It’s an interesting approach to rebuild the cars electrics (electronics) this way, are you going to use an EFI system and if so is this system “open” to integration? 

[cgriffin]

To start with I was planning to use the standard LS1 PCM just to get it started pre turbo.  They are fairly self contained and require very little tinkering to make them work.  I would however like to access a few of the sensors the motor uses just so I dont have to duplicate them for my electrical harness as well.  This is not very possible with the standard LS1 PCM as it has no CAN-bus and uses a very closed up OBD2 protocol. I hear the two opensource motor control systems (Megasquirt and VEMS) both will have a CAN-bus interface soon if not already (hadn't checked on it in a while).  Other than that I have no real plans of integrating motor control into my harness as the ultra high speed requirements and precision of motor control should fall to a purpose built high speed microprocessor.  It is in the plans to make my harness and the PCM talk and even report motor control faults to be displayed to the driver.

[ante]

Hi cgriffin,

As I said before, an interesting project which I like to follow. I am afraid I can’t help you much at least not at this point but please keep us posted with details along the way and maybe we can fill in some blanks for you! 8)