kicad-developers team mailing list archive

[André S. <list.dev.kicad@xxxxxxxxxxxx>]

Hi,

First: A visible hidden pin is a pin that has originally been hidden in the library and I set it to visible. Sorry for the confusion.

In my design (bug report here: https://bugs.launchpad.net/kicad/+bug/1443050) my own created part (PCM2906) had no hidden pins.
I then connected a power net named VDD -- used only on that sheet -- to some of the pins of that device.
Afterwards on another sheet I used a 4052 device from the KiCad library.
This one has hidden power pins which I set to display.
Then I connected a net +6V to its VDD pin.
According to the bug report this then is an explicit connection between VDD an +6V.

This was not intended and also at the time when I created that circuit I found some tutorial where explicitly was stated that non-hidden pins do
_only_ connect to the drawn wire on that pin (would be +6V in that case). Sadly I can't find that tutorial any more. At this time this
worked fine. (Maybe the older KiCad version had a bug and did it the "wrong way"… ;))

Also I understand that this is the current implementation in KiCad.

As I see it the current conclusion is that hidden pins are here to stay (for the time being). And I will not use KiCad libs that use them. Fine
and settled.

But it is a non-obvious and rather confusing thing to do. There are many people that get bitten by this "bug by design".

Therefore my proposal/strong wish that KiCad at least provides a way to check net connections and give an error when two nets with different
names are connected.

That KiCad internally uses net names different from the visible label is to no concern to me as a user. In my eyes KiCad must be able to detect
net name collisions regardless of intended or unintended.
It is for the user to decide if this collision is intended or an error on his side.
Silently connecting nets and also setting the resulting net name in the netlist "randomly" to one of the names of the different net labels is --
in my opinion -- not the "right way" to do things.

Regards,
  André


On 07.02.2016 12:44, jp charras wrote:
> Le 06/02/2016 18:23, André S. a écrit :
> > Ok, I see your point regarding not breaking old designs.
> >
> > However: the current KiCad broke mine, since it does regard hidden pins
> > different than "the old KiCad" (around 2013).
> > The old KiCad connected a visible "hidden pin" only to the connected net.
> > The current KiCad still connects it to "VDD" regardless of the connected
> > net and therefore connects two different named nets. Which then forbids
> > the use of "VDD" for a power net, when you use a KiCad library part with
> > hidden pins in your design and connect its power pin to a no-"VDD" net.
> AFAIK, about hidden pins, there is no change between 2013 version and
> the current version.
>
> There is no mystery:
> A hidden "power in" pin name (and only that) is seen as a global label.
> The only one difference between a true global label and a "power in" pin
> name is the fact a local label is connected to a global label having the
> same name inside the same sheet (call it an intuitive feature if you
> want), and this is not the case between a local label and a "power in"
> pin name.
>
> To tell the True, I do not understand what is a "visible hidden pin".
>
> Ant, as Wayne say, if you are not comfortable with hidden pins, just do
> not use them.
> But it is a basic feature for all ECAD I know.
>
> Using or not them is your choice.