kicad-developers team mailing list archive
-
kicad-developers team
-
Mailing list archive
-
Message #10086
Re: layer based constraints
hmmmmm... me again! Sorry about that, but I just had another thought I would
like to tell you:
Taking the layer constraints into the (net) constrain dialog would mean that
somehow, I have to tell for each constraint, to which layer it is
applicable.
One problem with this approach I have already mentioned: How is the "logic"
behind? What, if I am on a layer, to which no constrain is applicable to? I
think, I could tell a dozen other configuration, that would make us all
scratch our head and think: So, WHAT is no the actual with constraint for
THIS net on THAT layer?
In my approch: Simple. Net says: 6 mil. Layer says: 8 mil. Without thinking,
it's clear that it's 8 mils.
But there is another thing. Applicable to what? layer number? layer name?
What, if I change this? What if I (and i DID this in this very project)
decide to rename the layers, in a way that the naming increades from top to
bottom instead of from bottom to top (or vice versa, I don't know anymore).
What if I remove some layers? What happens to the entries already done?
Of course, these are all issues that can be managed. But I as a user then
asks myself: Hmmm. What about a net constraint applicable to a layer that
doesn't exist?
See what I mean? You can explain hot it is to be understood. But i think
it's WAY more difficult than just say:
Both net and layer constraint must be satisfied. Remove a layer? So, that
layer constraint is not used anymore. And therefore, it is removed from the
dialog. Very intuitive.
-----Ursprüngliche Nachricht-----
From: Simon Huwyler
Sent: Friday, April 26, 2013 4:08 PM
To: Dick Hollenbeck ; kicad-developers@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Kicad-developers] layer based constraints
One more thing: I agree that the additional numbers may confuse a bit. So,
why not just insert a check box named: "Use layer based constraints"?
Still one more thing (I'm a bit sarcastic now, but I don't mean it bad,
don't get me wrong): Why is the layer stack in the menu "constraints"? ;-)
-----Ursprüngliche Nachricht-----
From: Simon Huwyler
Sent: Friday, April 26, 2013 4:01 PM
To: Dick Hollenbeck ; kicad-developers@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Kicad-developers] layer based constraints
Hi!
Only a quite short anwer for the moment - maybe I have more time this
evening...
a) in my opinion, this should not be tied to layers. Instead it should
be part of a "net class" in the design rules. This would allow the user
to keep separate inner/outer constraints per net class. When
creating/modifying a net class, the user will be able to specify the
applicable layers (eg. [2-4,7,12]). This approach is also cleaner, since
all constraints will be in the same dialog window.
I'm not so sure about that, but maybe I just have to think again. The thing
is that we're NOT talking about NET constraints. Let's suppose I have the
following netclasses:
Power
50Ohm_Transmission_line
default
Now, in addition to the constraints based on these nets, we must apply
constraints based on the layers. So, what should we do?
default_inner: 8 mils, applicable to layers 2 and 3
default_outer: 6 mils, applicable to layers 1 and 4
What about Power? Say, we have (unrealistically) set this to 6 mils. What
now, if we place a power track on layer 3? What is the right constraint?
I still think, it's much more obvious to just say:
We have NET constraints.
We have LAYER constraints.
We must satisfy BOTH of them
The logical consequence is: They must be defined separately.
But as I said: Maybe I just have to think again.
b) why don't you make a "blueprint" in launchpad for this? I'm no expert
in how launchpad works, but it looks like the right tool for submitting
ideas and technical details.
Neither am I! :-) but I try to do it this week-end!
*) is the benefit of using the smallest clearance and spacing on the outer
copper layers
worth the this trouble in general? Are your boards really that busy on
these outer
layers? Seeqstudio is forcing you down a path that you do not have to
take. You can use
them by using the wider spacing in the inner layers, on all layers. What
are you gaining
really? Or is it just one part with narrow pad spacing pushing you down
this path?
In fact, the idea rised upon an urge! Yes, it's definitively a HUGE issue.
Not that I have such a dense design, but I have a fine pitch device! Nothing
special, just a 0.5mm QFP. But it won't fit into the inner constraints for
seeedstudio. So I could set the constraints to 8mils and live with the
errors. And with the fact that I don't use what I pay for.
An what is the trouble? As in C++ vs C: You don't pay for what you don't
need. Don't care about layer constrants? Leave them at 0. And, after all,
that's in the tradition of Kicad: Don't care about individual solder paste
clearance? Just leave it at 0.
*) next question is, who else needs this?
everyone that places a QFP device on a 4 layer print produced by
seeedstudio. :-)
*) the documentation would need to be updated if we were to go down this
path. Otherwise
we might get bug reports when somebody sees a different spacing on a
different layer for
the same net.
The beauty about my approach would be, that, if you don't acively insert a
number, nothing changes.
But I agree, this would need an update of the documenation. But I could do
this, too. And - after all - most additional features need to be documented,
aren't they? :-) And
To finish this response, I just want to stress again, that this was not just
an idea after thinking about what may bee a cool feature, but really the
result of some frustration that my real problem could not be solved
satisfactionally by the actual version of kicad.
Greets
Simon
-----Ursprüngliche Nachricht-----
From: Dick Hollenbeck
Sent: Friday, April 26, 2013 3:22 PM
To: kicad-developers@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Kicad-developers] layer based constraints
On 04/26/2013 03:02 AM, Dimitris Lampridis wrote:
On 04/25/2013 02:22 AM, Simon Huwyler wrote:
As some PCB manufacturers (i.e. seeedstudio) have different clearance-
an width constraints for outer- and inner layer, I had the idea to teach
Kicad to manage “layer based” constraints.
>
Ok, for the moment, I chatted enough. What do you think about it?
Hi Simon,
We use Kicad at work and we would like to get involved in the
development process, not only as a means to return something to this
excellent community, but also to actively improve the tools we are using.
To this end, I've also just subscribed to this list (hi everyone!), and
I'm keeping a list of features/fixes that I would like to start
proposing for implementation. I'm responding to your idea because it was
already on our list.
Now, back to your suggestion, here's my two pennies' worth:
a) in my opinion, this should not be tied to layers. Instead it should
be part of a "net class" in the design rules. This would allow the user
to keep separate inner/outer constraints per net class. When
creating/modifying a net class, the user will be able to specify the
applicable layers (eg. [2-4,7,12]). This approach is also cleaner, since
all constraints will be in the same dialog window.
b) why don't you make a "blueprint" in launchpad for this? I'm no expert
in how launchpad works, but it looks like the right tool for submitting
ideas and technical details.
Cheers,
Dimitris
Hi Simon,
I was thinking what Dimitris is thinking, before I read his post. Clearly
you took the
path that allowed you to get it working. And usually that is the best path.
But in this
case I think we can all see a certain discomfort in blurring what the layer
setup dialog
is for.
The first question I have is this:
*) is the benefit of using the smallest clearance and spacing on the outer
copper layers
worth the this trouble in general? Are your boards really that busy on
these outer
layers? Seeqstudio is forcing you down a path that you do not have to take.
You can use
them by using the wider spacing in the inner layers, on all layers. What
are you gaining
really? Or is it just one part with narrow pad spacing pushing you down
this path?
*) next question is, who else needs this?
*) the documentation would need to be updated if we were to go down this
path. Otherwise
we might get bug reports when somebody sees a different spacing on a
different layer for
the same net. Of course this happens on spin 2 of the board, after you have
forgotten
about the layer specific override and cannot figure out why that layer is
different.
As you can see, I am not taking a stand on need, only trying to see if it
exists.
Dick
_______________________________________________
Mailing list: https://launchpad.net/~kicad-developers
Post to : kicad-developers@xxxxxxxxxxxxxxxxxxx
Unsubscribe : https://launchpad.net/~kicad-developers
More help : https://help.launchpad.net/ListHelp
_______________________________________________
Mailing list: https://launchpad.net/~kicad-developers
Post to : kicad-developers@xxxxxxxxxxxxxxxxxxx
Unsubscribe : https://launchpad.net/~kicad-developers
More help : https://help.launchpad.net/ListHelp
_______________________________________________
Mailing list: https://launchpad.net/~kicad-developers
Post to : kicad-developers@xxxxxxxxxxxxxxxxxxx
Unsubscribe : https://launchpad.net/~kicad-developers
More help : https://help.launchpad.net/ListHelp
_______________________________________________
Mailing list: https://launchpad.net/~kicad-developers
Post to : kicad-developers@xxxxxxxxxxxxxxxxxxx
Unsubscribe : https://launchpad.net/~kicad-developers
More help : https://help.launchpad.net/ListHelp
Follow ups
References
