Re: gEDA-user: Managing parts multiple parts - physical part table feature request?

[Bob Paddock <bob.paddock@xxxxxxxxx>]

On Monday 30 May 2005 10:21 pm, natbuk wrote:

> As a librarian, I require a simple (minimal typing) method for entering
> zillions of parts that often look identical on the schematic except for
> some attributes (e.g. capacitors).

I asked a similar question last week; how does everyone manage their 
bill-of-materials.

> * for each library part (symbol), a text file (optionally) exists with
> property headings such as value, type, voltage, footprint etc.

A different file for a "zillion" parts would be bad.

In keeping with gEDA's ASCII based files  I was starting to put
my part information into a Open-RJ database.

http://openrj.org/

Open-RJ is a C, and other languages, library for manipulating a text file 
database.

> * each single physical part (one that can be ordered from a mfr) is
> represented by a single line in the text file

That is why I prefer Open-RJ as you are not limited to one line, per part.
I started down the Excel road and did not like where I thought it was headed.

> * there are two types of properties - I'll call them 'hard' and 'soft'
> (can't think of better words right now)
> * each physical part is represented by a unique set of hard properties -
> (unique so the netlist compiler can identify)

It should be a simple large number, containing no significant information.
I worked for a large contract manufacture for many years who tried to put a 
category to every part.  When you try to manage a inventory of 50,000+ parts 
you never really know what category to put something in, so mostly you found 
what you wanted in the huge "miscellaneous" category in the end anyway.

For example you have a mixed signal part, that is half digital and half 
analog.   You might find two parts from the same family, one in the digital 
category and one in the analog category, because two different people took 
out the part numbers at different times, for different customers.

You don't have to remember this number, as you never really see it after 
initial assignment, as the tools show you the text you are interested in.

> * soft properties are used to provide the designer with additional info and
> used by the compiler/bom generator for things like price, order code,
> footprint

Add to that list, beyond what you had in your original email:

A) Is there an alternate part that is the same in form-fit-function, it would 
link via the hard property to the equivalent part.  Bidirectional Link-Listed 
fashion. Manufactures love to obsolete things when you want to make products 
that have to be manufactureable for years.

B) Can this part be substituted?  If it can not be replaced because it is used 
in a FDA (pick your favorite acronym) device for some reason, it needs to be 
noted.

C) As a contract manufacture some customers  insist that you use only the part 
that they specify, even tho you have others of form-fit-function that would 
work.

As a Open-RJ database is a simple text file you can add/remove/replace items 
with your favorite tools.

> When the cadence netlist compiler runs, it cross references the hard
> properties which uniquely identify each physical part and can use

What is the format of Cadence's hard property?

> additional (soft) properties for items such as the PCB footprint. When the
> BOM generator runs, it also uses these files to extract any parameters
> (user defined), just like gEDA does, but as I understand it, gEDA requires
> the property to either have been added to the symbol during library
> creation or manually added on the symbol during schematic capture. 

Look at gattrib, in the gEDA distribution,  it maybe a good bases for your 
proposal.

> Keeping 
> things like PCB footprint 'soft' (e.g. could specify a different heading to
> be used as footprint to the netlist compiler) allows the use of multiple
> PCB design packages and existing footprints easily.

Sounds dangerous.  You will find no manufacture that has the same part 
numbered assigned to a part with multiple footprints.  This makes the hard 
link ambiguous.

> The main distinction between hard and soft properties is that because hard
> properties effectively become part of the schematic (or library), if you go
> and edit them and then try to compile an old design, the whole thing breaks
> - so one must be careful with the hard properties - but, the soft
> properties, because they are effectively linked during a netlist compile,
> can be changed at will and old designs remain good.

I agree with that, but not in the case of the footprint.
Old designs must always compile without user intervention.