kicad-developers team mailing list archive

[Karl Schmidt <karl@xxxxxxxxxxxx>]

On 06/24/2011 10:01 AM, Dick Hollenbeck wrote:
> On 06/23/2011 12:38 PM, Karl Schmidt wrote:
> > On 06/23/2011 09:29 AM, Dick Hollenbeck wrote:
> >
> > > Where?  What context are you talking about?  I think we need to store board and
> > > footprint files in both imperial and metric both.
> > Not that this is in error - but you should explain the 'why' as I'm in doubt.
>
> not both, but either or.  I still see footprints expressed in mils out on the
> web in datasheets.

Yes - but inches features can be stored in metric ( * 254 ) and reconverted to display in inch with 
no error - no reason to 'Store' them as inch with only one exception I can think of:  It would make 
it easier to edit mods that were edited and saved in kicad to later edit with a text editor - but at 
the cost of lots of added complexity ( you would have to track the unit of each feature). I can't 
think of any other situation where having kicad store in inch units makes sense. ( Someone could 
write a inch format export if there was a real need for it).

> > It seems to me that there will need to be a new Library definition extension so that both old an new
> > files can be READ in - I'm not seeing any reason to store in something other than metric?
> >
> > I'm thinking there could an M at the end of lines containing dimensional data that indicates it is
> > in the new nm standard? Thus old files are still compatible.
>
> I was thinking file specific units would be sufficient, I don't see a reason to
> each pad separately.  Maybe there's a reason to mark each footprint separately.
> But if we go too far down that road, the current file format is going to fall apart.

Good question - I can imaging where the pads were entered in inch, but drill holes or silk screen 
features are specified in metric. I think a line granularity of units would work and not break the 
current file format.

An example - there is a .025" feature - if it is stored as 635000 or 635000000 - the division to 
display in inch will always work with even results. If the mod is opened and some editing done to 
change some feature - kicad would need to track the unit of each feature to know which way to store 
it - why not just store it as metric once edited in kicad?




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Karl Schmidt                                  EMail Karl@xxxxxxxxxxxx
Transtronics, Inc.                              WEB http://xtronics.com
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