kicad-developers team mailing list archive

[Dick Hollenbeck <dick@...>]

Werner Almesberger wrote:
> Dick Hollenbeck wrote:
>
> > (units mil)
> > (resolution 10)
> > (const variable_def 30.4)
>
> Do you really need the resolution if you already have floating-point
> and a free choice of units ?

Probably not. It needs further thought. I duplicated something from 
specctra, and like all of this, the implementer would have to go back 
and justify each adoption by spending more time thinking about it.

> > We really don't need much in terms of expression support. Simple mx+b 
> > support is about all for positioning a pad with given shape.
>
> Yes, you usually don't need higher math. If you want to stay close to
> the respective reference material (i.e., use the same parameters as a
> basis), you may need to add or subtract distances and quite often
> divide them by two. Multiplications come in the form of
> dimension*integer or dimension*(integer+/-0.5).
>
> Things get a little more interesting if you want to create more than
> one footprint from a single definition, e.g., DIL/SIOC/SSOP/QFN/etc.
> families. Also, large BGAs are basically begging for some nestable
> loop construct.

I don't want to do that. Copy the part, add the pins. This can be done 
in a text editor with the enhanced copy and paste I suggested. The 
format must be simple and loops I think overstep this goal. By simple, 
I mean the footprint editor has to be able to edit the file in a WYSIWIG 
mode, i.e. graphical editing mode as now. I would not commit to coding 
the looping support. How do you name pins in a loop without 
introducing a reasonably rich programming language? Then such language 
is not easily editable in a WYSIWYG mode. 

We cannot make commitments for anyone else. So writing a specification 
without a commitment to code it is pointless. I am trying to suggest 
things I suspect somebody can code in short order.


Here is another important point:

The simpler the footprint file is, the more easy it is to use a text 
editor on it. In the end, a text editor is a tool that everyone is 
familiar with. Copying lines of text is easy.


In fact, I might even dumb down

(expr 0 + variable_def * 1)

to

(mx+b variable_def 1 0)

where "mx+b" would be a keyword, or maybe muladd.


> What's your opinion on measurements ? E.g., like here:
> http://kicad.sourceforge.net/wiki/index.php/Footprints

I think you mean "dimensions"? I like them, in particular when these 
footprints need to be printed to PDF or hardcopy. However, these 
measurements can be obtained in the footprint editor using the space bar 
to set a local origin. The cost benefit ratio of dimensions are too 
high for me personally to ever consider implementing them for free.


> But I think they were drawn manually, so there's no automatic
> correlation of the numbers displayed and the real distance.
>
> For comparison, all the measurements shown here are automatic (and
> adding a measurement is a matter of seconds):
> http://people.openmoko.org/werner/gta02-core/gta02-core-modules.pdf
How is this done? What software?



> > KISS. 
>
> Yup, as simple as possible but not simpler :)

Yes.


Dick