Problem when converting schematic to PCB

Software
1

Hello!

Something I noticed since V4 and for some reason I never asked.

Suppose you hav a circuit that you have finished routing. Then you notice
that some connection should be altered. For instance change a pullup to pulldown.
You make the change in the schematic, update the board…

In the following pictureL I have changed pin 22 to GDS. Originally pins 22 and 23 were
connected to VDDS, After the change and PCB update, the PCB software is aware of the
change, but doesn’t remove the corresponding link.
I remember that Eagle used to remove the last segment only. In this case it would skip the very
last straight line connecting pin 22 to the VDDS via.

Are there plans to change this in the near future?

Screenshot from 2023-07-18 09-10-28

Thanks!

2

I think you have been around this forum long enough to know the basics. I am certainly not a KiCad expert. But…KiCad flags an error in error checking when you have a pcb connection which does not agree with the schematic netlist. You don’t think that is adequate?

3

Hello!

Thanks for your reply.
That’s precisely because there are workarounds that I didn’t think or bother reporting this.
But for example, there is a way of removing all the chips that have been changed in the
schematic. Example, you change an OP amp to another one in the schematic, then in this
case you can configure the PCB software so that it automatically removes the previous one.
Similarily, in my example above, I think it would be nice without the connection the the via
since it knows it’s not connected anymore. And since this behavior already exists, I conclude
that it’s not beyond today’s technology.
Now yes, there are solutions, I know that. But I’m sure I’m not the only one wanting that kind
of functionality. Beside this, I don’t think it’s bad manner to suggest an improvement as long
as I do it politely and don’t ask to develop it by tomorrow morning.

4

Geez, kids these days are so spoiled. When I was an apprentice we used to have to get down on our hands and knees to scrub off the unwanted tracks with worn rags. :rofl:

What do you suggest the PCB editor do if the connection is part of the ground plane. Should it start modifying your zones?

5

Hello!

The only thing I suggest is that a connection disappearing in the schematic could also be
reflected to the PCB. But if you can explain why this idea is intrinsically wrong, I’m listening.

6

Hi,
in most situations I am happy that KiCad does NOT remove tracks by itself. However, it is recommendable to use the function : (sorry, german version !) “Werkzeuge/Leiterbahnen und Vias aufräumen…” after changing the circuit.

7

What do you suggest the PCB editor do if the connection is part of the ground plane. Should it start modifying your zones?

No, not zones. Only tracks. A zone would change it’s connections automatically at recalculation.

Coming from eagle (>25years) and now with 3years experience with kicad (and Altium and designsopark in between) I still find the eagle-solution better. With most usecases (my experience, on my projects with my workflow, may vary for others as Cris already pointed out) the deletion of a net in the schematic is followed by a deletion (or at least heavy rerouting) of the track in the board. So with the heavy schematic<–>board coupling of eagle the automatic track-deletion was meaningful.

But it doesn’t fit into the working-philosophy of kicad - and therefore I think this will not be changed (or introduced) in kicad. And I think it’s ok - forcing features (even if the feature is good) into a non-fitting environment will not always work.

8

I think self removing tracks would be a really bad idea. sure there are situations where it could remove the right segment but in most cases I can think of it would remove an unintended one. mistakes in the netlist also would be much more punishing as segments which were actually right would be removed.

while working with eagle I never liked that feature and I would claim it cost me more time then it saved me as in the end I often anyway had to remove/redraw wires to get to the intended routing.

9

Hello!

However, it is recommendable to use the function : (sorry, german version !) “Werkzeuge/Leiterbahnen und Vias aufräumen…” after changing the circuit.

Thanks Chris, I wasn’t aware of this functionality. It does what I want but needs a B command to
redraw the board.

Ich hab’s geschafft!

Allowing Kicad to do this automatically would be fine for me. But of course optional, with a checkbox
somewhere in the settings to keep everybody happy.

Thanks

10

Hi Roboya，

Good to see your analyze this kicad to design PCB,and compare with other design software ,maybe they got their own advantage,although I don’t quite knowledge in this field,also somehow get into it,anyway,i would like to know if there any new project to show up,and try to make it become final goods,what do you think of it?design concept is for utility,from virtual design to be reality,expect your reply,tks

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Where from KiCad should know if your intention is to have GNDS pin not connected to anything or VDDS to be not connected to anything by changing via net to GNDS and left GNDS pad connection to via.
Whatever decision KiCad would make I would understand it as program knowing better then me what I want what is what I most hate in any software.

2 Likes
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Hello!

Where from KiCad should know if your intention is to have GNDS pin not connected to anything or VDDS to be not connected to anything by changing via net to GNDS and left GNDS pad connection to via.

Sorry, I don’t get it!
For explanation purposes, I changed nack the design. I have set the pin 22 connection to its former state to take a picture.
So it used to be like this:
Screenshot from 2023-07-18 20-35-08

And it’s now like this:
Screenshot from 2023-07-18 20-34-21

So I changed the config pin FMSEL2 in the schematic. It used to be VDDS and is now GNDS. In the PCB above, Kicad now “knows” that pin 22 is connected to GNDS (and indeed kicad knows because the pin has been renamed “GNDS” on the PCB, and of course it was VDDS in the previous version).

Despite of this, despite the fact that Kikad “knows” that pin 22 which is FMSEL2 is now connected to GNDS, it still displays it as connected to VDDS.

Where from KiCad should know if your intention is to have GNDS pin not connected to anything or VDDS to be not connected to anything by changing via net to GNDS and left GNDS pad connection to via.

If I disconnect pin 22 (FMSEL2) in the schematic from VDDS and reconnect it to GNDS, how could kicad possibly not “know” that I want pin 22 connected to GNDS and not to VDDS?

And as I said above after Chris’ message: what he adviced works. I’m not saying it’s a wondertool
that works in any case, but at least it did exactly what I want in this particular case, and it did it even better than Eagle when I last used it. It removed the whole trace, then I just moved the via because there was no reason anymore to sit between 2 pins.

Screenshot from 2023-07-18 20-50-52

Whatever decision KiCad would make I would understand it as program knowing better then me what I want what is what I most hate in any software.

Time will tell me if this option is a good choice. This time it worked, and no error was generated
by the DRC. At least no error related to this change.

From what I observed with this command, Kicad does not pretend to know better than me, it did
exactly what I instructed it to do: remove connection to VDDS and add connection to GNDS, nothing more, nothing less. Maybe I will meet weird situations in the future where it will create a pure mess, but hey, that’s what backups are for.

13

Hello Jalina!

i would like to know if there any new project to show up,

Sorry, I don’t understand. Do you want me to share a project illustrating the problem I was talking about?

and try to make it become final goods,what do you think of it?design concept is for utility,from virtual design to be reality,expect your reply,tks

Be aware that I’m not a native speaker, and I really don’t understand your question.
Please try to rephrase.

R

14

No, that’s what swear words are for. :wink:

1 Like
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At your first picture there were no GNDS connections and I didn’t noticed that next pin 21 is also GNDS.

So read what I have written looking at it my way as in general case it can be such situation to be solved by KiCad. In that general case assume that pad 21 is not GNDS.
You had two pads connected to VDDS via to connect to VDDS zone at another layer.
Now one of them have to be connected to GNDS. I assumed that GNDS is also a zone at some other layer (for me GND is first to be made as zone at another layer then any VDD).
So KiCad should anticipate if:

  • you want pad 22 being connected by existing via to GNDS zone at another layer (so KiCad should change pad net to GNDS) and later you will yourself route pad 23 connection, or
  • you want pad 23 being connected by existing via to VDDS zone and later you will yourself route pad 22 connection.

In your case the decision is simple, but software have to be ready for general case. If there were no GNDS pads next to 22 and you planned to use that via as GNDS then disconnecting by KiCad pad 22 from via would be wrong decision. If software can make good or wrong decision I prefer it makes no decision at all and left me to make decision.

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I just wonder do you often design new project,and whether prototype to test quality,and how many do you need this kind of product?thx.

just wonder what is your design concept,design for what?tks.

17

Hello!

just wonder do you often design new project
That’s what I do for living, so let’s say 5, 6 projects a year.

and how many do you need this kind of product?thx.
I don’t need quantity. I do only prototypes. Usually 5 PCBs per version for one project.

just wonder what is your design concept,design for what?tks.

Sorry, I woudl like to reply, but I can’t figure out what a design concept is.
A customer asks me to design something, I do it. That’s all. Therefore first prototype,
build, test, correct bugs, second prototuype, etc. Not sure if its’ a design concept.

18

Hello!

No, that’s what swear words are for.

You got a point!

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