Re: gEDA-dev: netlist route styles

[John Doty <jpd@xxxxxxxxxxxxx>]

On Jun 3, 2008, at 4:22 AM, Peter Clifton wrote:

> On Mon, 2008-06-02 at 19:14 -0600, John Doty wrote:
>> On Jun 2, 2008, at 11:02 AM, Peter Clifton wrote:
>
>> What is "make" supposed to do with a dialog box?
>
> Nothing more than when it is expected to design your circuits for you.

I expect "make" to do what it does for software: propagate changes as  
needed. If I change the package of the default resistor in a project  
and type "make", I expect all data products for that project to  
reflect the change.

>
>
> Console based processing would have to work as usual, perhaps  
> throwing a
> stderr / stdout warning that there might be out-dated footprints for
> certain files.

Unacceptable. In a large project, such warnings are lost in the spew.

>
> There could also be a command line option / tool which specifically
> checks these things and returns 0 / 1 / whatever, so you can make
> further processing conditional on everything being "happy".

When I change a symbol to fix a pin assignment, part number,  
footprint, underlying hierarchical schematic, etc., I expect that  
change to propagate. Among other things, it's part of design reuse:  
in prototype maybe the default resistor is 0603, but in production  
it's 0201. Some customers imagine hermetic packages improve  
reliability, others are more sensible.

With symbol collections customized for the project, it's easy to move  
schematics from project to project (especially if you turn off  
automatic promotion of device and footprint attributes). So,  
low_noise_npn.sym represents BCX70K in an SOT23 in one project,  
2N930JANTXV in a can in another.

>
> In the case of divergent footprints / symbols which the user _wants_,
> I'd imagine the GUI action to express this would then take the desired
> symbol and dissociate it from the library copy, either giving it a
> different name, or just flagging so in the file.

It seems to me that *all* project symbols should be disassociated  
from the library copy and placed in the project symbol repository  
(often under another name: low_noise_npn, small_resistor, etc.). But  
embedding them in a schematic is a severe barrier to schematic reuse  
in an different project.

> There could be a
> hash-code of the confirmed version stashed in the layout / schematic
> which just ensures no further prompting unless the library version
> changes again.

The library is really only useful as a starting point, mostly for  
graphics. A project has its specific requirements that drive the  
device, footprint, and other part specifications. A schematic may be  
reused in several projects with different parts requirements. Keeping  
the part specs in project-specific symbols facilitates this. Gattrib  
is useful for the occasional exception (sometimes you can't shrink to  
an 0201), but is too time-consuming for managing common attributes in  
a big project.

>
>
> -- 
> Peter Clifton
>
> Electrical Engineering Division,
> Engineering Department,
> University of Cambridge,
> 9, JJ Thomson Avenue,
> Cambridge
> CB3 0FA
>
> Tel: +44 (0)7729 980173 - (No signal in the lab!)
>
>
>
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John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd@xxxxxxxxx




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