Electronics > KiCad

why is KiCAD not following rules for nets. VDD turns into GND

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janoc:

--- Quote from: JPortici on November 21, 2023, 10:15:23 am ---i agree that "nets that overlap each other for whatever reason get merged" is annoying but it's far from being a dealbreaker, that is an user error anyway, so it's far down in my list of complaints.

--- End quote ---

I am pretty sure that is not the case in KiCAD - two overlapping wires don't get merged. The OP has most likely either put the connection dot between them or connected two wires to the same pin and then KiCAD assumes you do want to have these things connected and will put that dot there for you.

Either way that's a user error that KiCAD has no way to know that it is not what you have intended.

JPortici:

--- Quote from: janoc on November 21, 2023, 12:12:40 pm ---
--- Quote from: JPortici on November 21, 2023, 10:15:23 am ---i agree that "nets that overlap each other for whatever reason get merged" is annoying but it's far from being a dealbreaker, that is an user error anyway, so it's far down in my list of complaints.

--- End quote ---

I am pretty sure that is not the case in KiCAD - two overlapping wires don't get merged. The OP has most likely either put the connection dot between them or connected two wires to the same pin and then KiCAD assumes you do want to have these things connected and will put that dot there for you.

Either way that's a user error that KiCAD has no way to know that it is not what you have intended.

--- End quote ---

they don't get merged when you draw them, but when you move/rotate stuff and they happen to overlap. That is annoying but can worked around pretty easily

ebastler:

--- Quote from: janoc on November 21, 2023, 12:12:40 pm ---I am pretty sure that is not the case in KiCAD - two overlapping wires don't get merged. The OP has most likely either put the connection dot between them or connected two wires to the same pin and then KiCAD assumes you do want to have these things connected and will put that dot there for you.

Either way that's a user error that KiCAD has no way to know that it is not what you have intended.

--- End quote ---

The OP has long since figured out that he made a wrong connection in the schematic. It's actually right in the first post as a later edit:


--- Quote from: coppercone2 on November 13, 2023, 04:14:08 am ---Oh, ok. I wrote this out and then I figured its trying to help me, cryptically. There was a short through a diode on the ass end corner of a schematic bridging things. I guess it would be nice if it told you plausible short circuit. Maybe it does in the ERC but I Have like 999 problems there. The sky is falling because of some floating N/C pin but the short circuit between VDD and GND is hidden on priority #485

--- End quote ---

Which then led into an extensive discussion of the fact that Kicad's ERC does indeed show many errors if the design has many errors, and whether or not that is a good thing...  ;)

Kleinstein:
If there is an unintentional conncetion in the schematics, the ERC may not even catch the problem. For the program it is hard to decide if the link is intended or a mistake.  So it would not be about having to picky an ERC but possibly an ERC that could give even more warnings.  There could still be a warning (e.g. like both ends of 2 pin part connected), but I don't know.

When doing the layout one would normally notice such a fault at least.  So some manual error check is still a good idea.

ebastler:

--- Quote from: Kleinstein on November 21, 2023, 05:28:56 pm ---If there is an unintentional conncetion in the schematics, the ERC may not even catch the problem. For the program it is hard to decide if the link is intended or a mistake. 

--- End quote ---

Well, in the present case the ERC would certainly have detected the short between GND and VDD. :)

And it detects clashing outputs as well. Actually, I don't think I have managed to sneak an unintended short past the ERC yet. But it is certainly possible, e.g. with bi-directional signals or parts where the pin properties are poorly defined.

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