DRC: Missing connection between items

Hi there KiCad folks.

I am down to my last DRC error and it’s really causing me to lose the will to live. It’s claiming that one of the pins on my IC that should be connected to the (digital) groundplane is not connected. You can even see the curved ratsnest going off the the left from pin5 (GNDD).

However, on close-up inspection it certainly seems like the pin is connected to GNDD. I tried deleting the GNDD zone and re-creating it - same problem. The other GNDA pins on the north side of the IC connected no problem at all to their GNDA groundplane. Please please please somebody put me out of my misery.

KiCad has no way and logically can’t have any way to give information about unconnected items which would correspond to some mental representation of connections in the user’s mind. In reality there are possibly two groups of items. One group is where the GNDD pad 5 is connected to. The other one where the zone belongs to. From the screenshot it’s impossible to tell if that zone is connected to other items; probably it is because it has been filled. KiCad just tries to find the shortest distance between the two groups, in this case between the center of the pad and the edge of the zone.

The best way to connect those two groups of items together may be elsewhere, and you have to find it yourself. Software just can’t do it for you (an autorouter might be able to do it, but it wouldn’t know what is the best way from the standpoint of the whole design).

KiCad could of course give a more informative message, something like “Net GNDD is split into two separate parts which need to be connected”. Choosing two items randomly isn’t often very helpful.

EDIT: I’ll write a wishlist issue for this.

2nd EDIT: Other people have thought about this, too. I added a comment. pcbnew: DRC - unconnected pads should not be shown as pairs (#7416) · Issues · KiCad / KiCad Source Code / kicad · GitLab

Hi eelik,

Thanks for responding. It’s true - there are two zones GNDD and GNDA, which are joined at the tie which is visible. From the little X thermal relief connections, you can see the tie is connected to both planes. The GNDA pins on the top-side have rooted sucecssfully into the GNDA zone, and there’s just one GNDD pin in the bottom zone (of many other GNDD connections) which just refuses to see that it IS connected - I can see the strain relief X.

So if the problem exists elsewhere - what am I looking for? Is it safe to ignore the warning? (I’m sure I know the answer). I’m at the point now where if the PCB turns up without proper GNDD connection on that one pin I would happily solder it myself.

I did not allow the ground-plane GNDD to create islands, so I know it’s not split. All items connected to GNDD simply attached themselves into the ground plane except for this one pad (which actually appears from the copper as if it IS connected).

This is my first use of KiCad and I had such high hopes.

You are right. Now that you mentioned it - it’s obvious! There is an island in the GNDD zone, and the offending pin is planted into the island!

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