i am using kicad version 6.0.2, i am setting custom rule for diffrerntial pair. i want to assign different trace width, diff pair gap & clearence to individual nets.
I have tried this.
(constraint diff_pair_gap (min 0.4mm))
(constraint track_width (min 0.1mm))
(constraint clearance (min “0.05mm”))
But i am not getting result for specific net.(condition “A.inDiffPair(‘USB’)”).
How can i assign the constraint to a specific net?
I haven’t tried this myself yet, but maybe the answer is in this thread?
I tried this one also but still it is not working.
don’t use “USB” use “/USB”
Trird this one also but still it is not working.
Try the same rule that you put, your problem is the name of the differential pair, if you use “USB_P” and “USB_N”, your selector must be “USB_”
Your rules worked for me if I added an
(opt <desired value for the router to use>) token to the
max are used by DRC only, and
opt is the value that the router uses when you’re routing.
So I did:
(version 1) (rule "diffpair" (layer F.Cu) (constraint diff_pair_gap (min 0.4mm) (opt 0.43mm)) (constraint track_width (min 0.1mm)) (constraint clearance (min "0.05mm")) (condition "A.inDiffPair('/usb_')") )
With those rules the router automatically put the traces 0.43mm apart, regardless of what I had set in the netclass DP settings, and DRC was clean. I found the Constraint Resolution tool to be really helpful here - initially I had the diff pair name wrong and it told me that my rule was not applied to the selected trace, which tipped me off to the problem.
P.S. I didn’t check the track width and clearance but I think those would also be set automatically by the router if you put in an
opt token to those constraints.
Thank you for the reply.
I tried same thing but it is still not working.
I am using kicad in ubuntu, so is there any issue regarding OS?
I doubt this is OS-specific. Could you share your design, stripped down if necessary?
At least sharing a screenshot of the traces and net names would be helpful.
Alternatively you could assign your differential pairs to a dedicated net class and then substitute
(condition "A.NetClass == 'your_netclass'")
Thank you @Kharar
I tried this one & this is working properly.
(constraint diff_pair_gap (opt 0.1mm))
(constraint track_width (opt 0.1mm))
(constraint clearance (opt 0.1mm))
(condition “A.NetClass == ‘Diff_100_OHM’”)
You are welcome @Jay_Khandekha
Now for the mystery of why the other approach didn’t work for you:
As you can see above I have a differential pair named
TD0_P that are defined from a sub sheet named
LAN, so in order to use the name correctly I would have to include the path prefix.
If this doesn’t help can you maybe find your net and post us a screenshot of that, like the above?
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