CAN BUS test

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CAN BUS test

Postby Jabsam » Mon Nov 26, 2012 6:32 am

Hi All.

Do you think this Can Bus signal is correct? Thanks.
can bus.jpg
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Re: CAN BUS test

Postby Alan » Mon Nov 26, 2012 6:31 pm

Not totally sure to be honest. CAN Low looks good - switching cleanly from approx 2.5V to 3.5V

CAH H is switching from about 1.3V to 2.3V so a little on the low side. The lack of high frequency content compared with the other channel makes me wonder if something is loading the signal a bit.

I dont think whatever is different with CAN H is enough though to cause any errors in communications.

Hopefully someone with more experience than me can comment further.
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Re: CAN BUS test

Postby Darren Cotton » Mon Nov 26, 2012 7:08 pm

First look seems OK, however, Can you post the psdata file please

What has made you check the CAN?


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Re: CAN BUS test

Postby Jabsam » Tue Nov 27, 2012 6:08 am

The waveform is from a Buick car.

The CAN H & L look like normal. Sorry the picture in my post above, I activated filter on Ch B.

I most interest in why the one part of CAN H excessed 3.5 V (and one part of CAN L less than 1.5V). But while I disconnected the EBCM and VES, the CAN Bus swictched normally as standard(CAN H 2.5-3.5,CAN L 1.5-2.5).
pic.jpg


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Re: CAN BUS test

Postby Darren Cotton » Tue Nov 27, 2012 8:20 am

The peaks at the end I see as normal, end of data message... The reason when removing the nodes the CAN changes is maybe because the message data is not being transferred

I see nothing wrong with the CAN

CAN  GOOD.gif



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Re: CAN BUS test

Postby Jabsam » Wed Nov 28, 2012 1:00 pm

Hi Darren,

Thanks for your reply. Could you please explain that why the end of data message have peaks more than 3.5 Volt for CAN H & less than 1.5 Volt for 1.5 for CAN L?
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Re: CAN BUS test

Postby Darren Cotton » Wed Nov 28, 2012 1:32 pm

This is the acknowledgement section of the data frame. Its Normal.....


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