CANBus/logic analyzer guru needed?

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Eli

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Oct 9, 1999
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Maybe? Pretty please?

I've got a project that I can barely get off the ground because I don't really know how to use the logic analyzer to capture the CAN traffic... lol. I keep getting Bit Stuffing errors or something. I'm really not very good at the bits and bytes stuff and am fairly lost.

Monetary compensation in exchange for help would be fine; I expect this could turn into a bit of a longer term project. I just don't know what I'm doing! Maybe I just need a different or better logic analyzer - maybe someone has some recommendations there?

Since a pic is worth a thousand words:
001_1024x768.jpg


Although in this case it might cause more questions than it answers. o_O
 

Eli

Super Moderator | Elite Member
Oct 9, 1999
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Hmm. I thought this was a geek forum. ;)

Let us not forget about the monetary compensation part. Nobody could use a few extra bucks eh? Easy money for the right person I'd bet.....
 

serpretetsky

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Jan 7, 2012
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Are you located anywhere near San Jose area? I'm not a guru, but I am student for computer engineering and I would be interested in seeing what you are trying to do (not for monetary pay since Im not a pro).

May I ask what the exact error you are getting is?
 

polarmystery

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Aug 21, 2005
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Can you take a screenshot of the PC that is capturing the data? I'm not a CAN Bus expert, but I am a digital design engineer. I could probably make sense out of what you are seeing.
 

Eli

Super Moderator | Elite Member
Oct 9, 1999
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Eek - Thanks for the replies guys. My week blew up and I kinda forgot about the thread.

Are you located anywhere near San Jose area? I'm not a guru, but I am student for computer engineering and I would be interested in seeing what you are trying to do (not for monetary pay since Im not a pro).

May I ask what the exact error you are getting is?

I'm not in San Jose unfortunately, although I do have a business partner down that way.

I'm not sure what the error I'm getting is. I don't really even know how to set the software up lol. I guess I should play with it again. It seems I was able to get Received data, but not Transmitted.. I was getting bitstuffing errors on the Tx side.

Can you take a screenshot of the PC that is capturing the data? I'm not a CAN Bus expert, but I am a digital design engineer. I could probably make sense out of what you are seeing.

Sure, I'll try and do that.



That looks awesome, thanks a lot. I'd rather give the $450 to someone here using the hardware I already have, but I'll explore that option if I have to. It looks perfect.. Hmm..... I'll give it a week. ;)


In case it wasn't clear, I'm trying to monitor the communications between a Honda computer and some Honda software so I can figure out the commands being sent to query the data. I want to be able to query the data with my own device, ie: an Arduino.
 
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uclabachelor

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Nov 9, 2009
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I have an oscilloscope that can do CAN bus decoding (socal area) that would make debugging and development a breeze.
 

Topweasel

Diamond Member
Oct 19, 2000
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Sorry can't help here, I work for a company that's pretty big in the CANbus communication market, as an IT guy outside the basic idea of what it is doing I don't know anything about the communication protocols to be able to help.

I could try to ask an engineer or two if I knew more specifically what you were running into.

I am wondering if you might be running into an issue with not using the right transiever type at one of the points. I know for the year or so I worked in phone support that would often be an issue if you were using a transiever for high speed CAN on a low speed or vice versa.
 

serpretetsky

Senior member
Jan 7, 2012
642
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I'm not in San Jose unfortunately, although I do have a business partner down that way.

I'm not sure what the error I'm getting is. I don't really even know how to set the software up lol. I guess I should play with it again. It seems I was able to get Received data, but not Transmitted.. I was getting bitstuffing errors on the Tx side.
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There are various reasons to do bitstuffing, from what I'm reading on wiki, for CANBus it's used to provide a changing signal so that the reciever can resynchronize it's clock.

Under such a situation, a transmitter will add an extra bit of opposing data any time there are a number of consecutive bits causing an unchanging signal. That also means that the receiver expects to never get more than a certain amount of consecutive bits. If it does get more than the expected amount, then that is an error.

The first thing I would check is make sure your BAUD rate on your software analysis program is the same as the BAUD rate of the CANBus system.

Apparently the BAUD rate on a CANBus system is set using BRP, TSEG1, and TSEG2. I have no idea what those are, but this guy does:

http://www.jguru.com/faq/view.jsp?EID=242031
So if you know those values you should be able to find your BAUD rate and adjust your software accordingly.

edit: Ohh, i want to reiterate that I don't know anything about CANBus specifically, just trying to help with what I do know. :D
 
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