kicad-developers team mailing list archive

[Wayne Stambaugh <stambaughw@xxxxxxxxx>]

On 1/20/2015 10:51 AM, Tomasz Wlostowski wrote:
> On 20.01.2015 16:19, Wayne Stambaugh wrote:
>> On 1/20/2015 12:44 AM, LordBlick wrote:
>>> In response to a message written on 13.01.2015, 19:20, from Tomasz
>>> Wlostowski:
>>>> Hi all,
>>>>
>>>> During my work on diff pairs/matched length tools, I've encountered a
>>>> rather tricky problem: as the diff pair gap specific to a particular
>>>> pair of traces is stored nowhere, the shove algorithm will mess up DP
>>>> coupling after saving and re-loading the board. Ergo: the DP gaps (and
>>>> possibly other settings) need to be stored somewhere in .kicad_pcb
>>>> files. Perhaps in a yet another s-expr token.
>>>>
>>>> The problem is that adding any new token to the file format causes all
>>>> precedent versions of pcbnew to drop an error attempting to load the
>>>> file. I would propose two solutions to overcome this:
>>>> - (a dumb one) if the version in the file header is newer than the
>>>> version supported by the running application, issue warnings instead of
>>>> fatal errors on unknown tokens,
>>>> - (a bit smarter) enclose all optional tokens in a "minimum" version
>>>> block ( min_version version_number ( optional_token ( ... ) ) ) that
>>>> would be ignored if the application version < version_number.
>>>>
>>>> I consider this modification quite important from the point of view of
>>>> adding future features and the upcoming stable version: if we keep
>>>> things as they are, adding any new feature will either make the files
>>>> unreadable to the stable version or force us to support saving in
>>>> multiple format versions.
>>>>
>>>> Looking forward to your feedback,
>>>> Tom
>>> I think that may be sufficient to add section [gal] to .pro file as
>>> usual project setting. In this way you can avoid the next .kicad_pcb
>>> format version change.
>>>
>>
>> I'm not terribly thrilled about that idea.  One of the things we have
>> changed over the years is to move board specific settings out of the
>> project file and into the board file.  This makes the board file more
>> portable. 
> 
> Hi Wayne,
> 
> Fully agree here. What I meant when I started this thread was defining a
> way to store more complex DRC constraints than simple clearance/track
> width. The current model can't handle differential pair and constrained
> trace length. Such parameters surely belong to a PCB design, so their
> place is IMHO in the .kicad_pcb file.
> 
> Anyway, for the first release of the new P&S features, I'm not going to
> modify the file format.
> 
> Cheers,
> Tom
> 

Hey Tom,

If it is important to save the design settings, now would be the time to
make any file changes rather than after the stable release.  We know we
are already going to have issues with users who upgrade from the current
stable release due to layer name translations and the 32 to 64 layer
transition.  I would rather get it over with now than drag it out over
the next development cycle.

Cheers,

Wayne