Since this project is really about controlling the VGT turbo... I have a few thoughts..
First off...
How about scrapping the CAN bus altogether? Tear out the electronic controls from the box, and connect a stepper driver from the arduino directly to the stepper of the control? I'm sure we can build a more robust circuit, and it'll be in a more friendly environment as well.
Is there a sensing pot on it somehow that returns the actual position? Wire that back to an input... The shaft speed sensor would be the only hanging point perhaps.
Secondly.
When I was playing in VB to rough out my project code, I made it so that the default position was always closed, and then everything else forced it open.. it would be much easier to add hysteresis to it that way so that it can always open in whatever increment it needs at whatever rate is needed, but it would only close at a predetermined step size and/or rate
Someone needs to find (*cough* buy *cough*) me a VGT turbo to play with.. I've been scouring Craigslist for some and haven't had any luck.
What's the going price on used VGT's?
You're going to want to use the stock gearbox, it isn't bad and the CANBus components don't cost but like $20 on the board.
Not only is it simple to talk to, but it actually has a built-in circuit to maintain position as backpressure increases.
Ah, OK... I guess we have to figure out just how often and how much we can update it before it overheats. I was still thinking of using the stock gearbox, just not the electronics of it.
I guess I'm going to have to get the CAN bus components after all... shoulda kept them in my order!
If you get my shield... it kinda saves you the $25 of getting a different shield.. and the wiring doesn't suck ass.
Who would use a RS232 cable > 4 pin turbo connector ?
So then you end up having to de-solder the 2 screw pinch setup, and wiring direct.. which now no one wants your CANBus if you don't need it.
You could however, bread board a canbus setup, just need the 2 ics 2 resistors, and a 16mhz crystal. You can download seeeds's canbus schematic for more exact details on setting it up, but the MCP ic's come in PDIP / DIL through holes :-D
I've personally ran the gearbox without water, and <1ms updates in my first week of code iterations, and didn't seem to have any gearbox problems. YMMV thou