Need info on CAN bus

[ptribbey]

I am trying to figure out the Controller Area Network spec. Specifically how would one connect a picaxe or another processor to a GM airbag controller.
I do not have the pinout of the GM controller. I guess that is a place to start.
Has anyone done this? I know one can buy very expensive computers set up for this type of thing. My goal is to read the crash data from a number of controllers I have accumulated from an auto body friend of mine. He replaces them while refurbing the auto. I have successfully powered up the unit and probed the processor for clock signals. I am wondering if I need to order a dedicated CANbus IC to interface to my master controller? Inside the controller is what appears to be a processor, outboard eeprom, a voltage multiplier, a power amp and various other electronics. They all appear to be numbered with proprietary numbers.
Please reply if you have any relevant info.
Thank You
Paul

 

[BeanieBots]

A PICAXE cannot talk directly with CAN bus.
You WILL need to get a dedicated chip. Your best bet is to get one which converts to RS232 but check that it is at a baud rate and data rate that a PICAXE can cope with.

 

[RexLan]

I "suspect" that the Picaxe is too slow as well.

 

[ptribbey]

Question about soldering irons

Would a few of you please tell me what soldering iron you use for the smallest smd? I use a 40 watt Weller exclusively, but realize I need to make a purchase to get the small stuff. Inexpensive is a plus. Geez some of that stuff is small. It seems to me a person would need a very small tip.
Thanks for your help
Paul

 

[papaof2]

You might start with the data available at the SourceForge site on CAN:
http://sourceforge.net/projects/can/[URL] Also check the Yahoo groups that discuss CAN bus: [URL]http://groups.yahoo.com/phrase/can-bus-interface

I did some research a year or so ago and decided that one of the kit or built interfaces would be the easiest way to interface with the CAN bus. Most of the serial devices communicate at 9600 baud (and up), so would require a higher end PICAXE to handle the data (there can be a LOT of it).

For general automotive use, it's easier to use one of the kit/built interfaces with a PC (serial & USB interfaces available) because of the amount of data returned. A PICAXE may be adequate for looking at a single device.

John

 

[Dippy]

I'm not a few, just one.
For quick smd proto work I tend to use a 0.12mm Mallory tip on an Antex solder station iron.
For TSOP I also use a COIL x7 eyepiece and I've developed a squint
I apply the paste, dab the component on and place the tip/bit near the leg. The joint is usually done in about a second (man!).

I know you can get 'proper' smd tips for some irons, but I'm not a fan.
Other people have other preferences... and good luck to 'em!!

Some PIC 18Fs and above have specific stuff for CAN. And so, you will need a nitty-gritty compiler. You will also need experience of reading real details in PIC Data Sheets - unless you can steal the software.
If you struggle with PICAXE BASIC, then get someone else to write it.
If you can get a CAN interface chip, then feel free to have a go.