Questions about Kicad's ERC checking


I find the ERC reporting very “noisy” and can’t see a way to reduce the number of messages for my preference.

The only ERC messages I am really interested in are where there are nets that are only connected to one pin. So, let’s say I have placed two labels as follows:

RXD0 and RXDO. One has a zero on the end and the other a letter O. They look very similar, but I would like a message telling me this is an error.

Similarly, I would like it if I place a new label on one end attached to a pin, but it’s not connected anywhere else.

Now, I know that this latter type of error is flagged up, but the problem is there is so much noise for things like unconnected pins on, for example, the processor, that it is just too easy to lose a legitimate problem.

Is there a way of not checking for unconnected pins, but checking for nets that are only connected to one pin?



If ERC is “noisy” then you have problems. You should end up with no messages at all. If you have unconnected pins then mark them as unconnected.

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Going and clicking no connection on all the pins is a pain and will be distracting on the schematic. There should be a better way of doing it than that.

In Eagle, you can leave the pin as is, and I don’t think the ERC flags it as unconnected. I’m not sure that is better, I think I prefer the KiCad method.

If you have a better method, can you suggest it?

In the CAD system I’ve used over many years you could simply switch off reporting of unused pins while flagging nets with one or no connections. (You just don’t seem to be able to switch off any of the tests you don’t want in kicad.) That serviced me very well and I would definitely prefer that. I’ve only casually used Eagle for looking at other people’s schematic, so I can’t comment on how that does it.

To my mind there are often so many pins on a schematic that aren’t connected, you don’t want that reported. Well, I don’t! :smiley:

The no connections error would be more like a floating label in the case of kicad through I think. I’m used to using pcad Master Designer that names a net and doesn’t have it depend on a label being placed upon it (ie the net has the same name assigned to it, even if you delete or move the label). I shall really miss that method of doing it. Slightly tangentially, I shall really miss how pcad warns you that you are assigning a net name that is already assigned to a different subnet. I’ve never found any other CAD system that has that lovely feature.

The flip side to this, is that I’m on my third board with kicad and it does most things really, really well. I prefer it to Altium actually which is a hugely expensive piece of software. In general it’s a very intuitive application and there’s a lot of excellent help around for it as well as masses of parts and symbols.

In the ERC Options dialog, you can select error/warning/none for each combination by clicking on the icon (E - W or green box). I think I discovered that by accident…

I think it would be useful to have a category for “single connection nets” as well.

I already tried that. Even if I set everything to green I still get certain errors reported.

I prefer the piece of mind that comes from double checking each non connected pin as I flag it not connected. Allowing those errors to be muted makes it much easier for a missing connection to go undetected.

I don’t think it is at all distracting on the schematic, the NC symbol shows intent.


Yep, I fully respect that. I was just hoping I could tailor it to my preference. I’ll get used to it in time, I’m sure.

Nobody likes to be nagged by an ERC that repeatedly asks, “Do you REALLY mean that?”, but I’ve made enough mistakes over a lifetime that I appreciate having an automated tool that watches out for me. Yeah, the “No Connection” symbols DO clutter the schematic a bit - perhaps there’s a less intrusive way to show this information.

I understand the request by @DiBosco to customize the level of ERC and agree that some users would find this helpful. (The same concept could be applied to the DRC in PCBNew.) As I work through a design there are often waypoints where I’d like to check the work I have completed, knowing that some things still need to be done. I KNOW there will be warnings and errors related to the remaining incomplete tasks, and it would be helpful (“Reduce the noise”, as @DiBosco put it) to disable some types of error checking while I make sure that the work already completed is error-free.



I think at the moment, it is just a “quirk” that you are not accustomed to. I LIKE IT! … even though it was never on any of the “professional” schematics I have read. It is a nice addition that makes good sense.

If you do some reading/Googling, then it will be easy to see that it is generally bad practice to leave pins disconnected.

^^^THIS! It means that there is a REASON why the pin is NC.

I have parts on my board where NC is required, and where NC is not recommended. Having the NC explicitly shown on the schematic is a nice thing.

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@Spring, I take your point and it’s great that you like it. However, I’ve been professionally designing schematics, laying out PCBs and writing embedded code for thirty years and in all that time I have not one single time had a board error because a pin was left unconnected. It is, for me, totally unnecessary. Therefore, it would be a good thing, if the option was there to switch off the reporting of that.

As for leaving pins unconnected being a bad practice, that is only partly true (and something after thirty years of electronics design I do not have to google TYVM :yum: ). Logic inputs, for example, shouldn’t be left floating, but there is absolutely nothing wrong with leaving op amp outputs, processor GPIOs and a myriad other pins unconnected.

There are numerous ways to skin the CAD rabbit and it’s good to have the flexibility to allow different people to do it how they want.

Unfortunately KiCad is written with the rest of us mere mortals in mind. We may not need the feature any more than you do but it is a small price to pay for a little extra piece of mind.

In any case, we here on the KiCad forum are just users like yourself. We can express our opinion but we have no say when it comes to making changes to KiCad. You’ll need to register your feature request as a “Wishlist” item on the bug tracker.


Happy I found this thread, now I know Kicad is not for me.

May I suggest this information go hi on the documentation, so those of us for wich this is a showstopper, dont use time on Kicad.

IMHO software should help and support, not Harass users.

I would not state that ERC harasses users. After all you need to explicitly trigger it.

Is it lacking in features? Yes of course. This is why version 6 will most likely get a more powerful ERC system. It remains to be seen how exactly it will look like. I would suspect this will also contain a way to disable the check for unconnected pins.

According to -> the link to the specification, this seems to be the plan.


Totem, any CAD system you use will have things you don’t like. I think you are making a mistake calling this a show stopper. Kicad has more than enough excellent features, a great UI, reliable easy to use work flow, massive support form the community, huge number of symbols and footprints including 3D models and is free in both senses of the term. I think it is shorted sighted to say this issue makes it unusable.

I say this as the OP who was asking about it in the first place.

Go and try and use something like Cadstar, Altium or Eagle which have far more WTF kind of foibles with them and you soon appreciate just how good Kicad is. On top of that they are all varying degrees of expensive. Sometimes you have to be pragmatic and you definitely need to appreciate the work people put in to provide you with excellent open source tools.

Is it so big problem for you that there is the function others like to run? No one forces you to run ERC.
I have never run it and am happy with it :slight_smile:

Thanks for your comments.

I believe the world is big enough for all of us. You like Kicad, good for you, I dont, so I find something else.

I will not use software that bosses me around, i feel Kicad is doing just that.

You can of course find software which fits your workflows and habits better. That’s good.

Good luck trying to find software which doesn’t “boss around” users at all. It’s impossible even theoretically until software can read thoughts and bypasses human cognitive and emotional abilities.