Author Topic: Signal integrity on CAN-Bus - Eye Diagram and Eye Mask  (Read 4043 times)

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Offline OzeTopic starter

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Signal integrity on CAN-Bus - Eye Diagram and Eye Mask
« on: October 25, 2021, 08:26:30 am »
Hello everyone,
I am a long term viewer of the EEVBlog but finally I need the help of this awesome community. I'm currently struggling with the measurement of the signal integrity of a low speed CAN-Bus network (125 kbit/s).
I want to measure the signal integrity using an eye diagram on my Oscilloscope (R&S RTB2004). Therefor I've connected a differential Probe on the CAN-H and CAN-L lines and activated infinite persistence on my Oscilloscope. I got a beautyful eye diagram on screen but now I don't know how to determine if the siginal integrity is still ok because I don't know where to get an Eye Mask for the CAN-Bus with 125 kbit/s. So can anyone provide a way how to determine the shape of the valid region so I can determine if my signal integrity is ok or not?

Thank you so much

Oze
 

Offline thinkfat

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Re: Signal integrity on CAN-Bus - Eye Diagram and Eye Mask
« Reply #1 on: October 25, 2021, 08:34:26 am »
You need the recovered bit clock as a trigger, otherwise it'll be just a pretty picture on the scope screen.
Everybody likes gadgets. Until they try to make them.
 

Offline dietert1

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Re: Signal integrity on CAN-Bus - Eye Diagram and Eye Mask
« Reply #2 on: October 25, 2021, 09:01:52 am »
I think CAN is an application of RS485. https://www.ti.com/lit/an/slla375/slla375.pdf has some introduction.

Regards, Dieter
 

Offline Leo Bodnar

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Re: Signal integrity on CAN-Bus - Eye Diagram and Eye Mask
« Reply #3 on: October 25, 2021, 05:38:56 pm »
If you have access to one of the devices, trigger on the signal going into CANbus phy (TX line)
Leo
 
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