gEDA-user: Musings on attributes

[Ales Hvezda <ahvezda@seul.org>]

[ Ales here, I'm reposting this since majordomo didn't recognize the
  e-mail as being subscribed to the geda-user mailinglist. ]

[ Hi Theo, 

  Interesting.  I like the idea of a comment inside of the symbol,
  though I don't know if I want to start creating lots and lots of
  attributes like value_comment= or footprint_comment= or device_comment=.
  I like the idea of a plain comment= attribute.  This will allow for
  permanent comments inside of symbols.  In fact, Werner Hoch has been
  using comment= for marking certain symbols as bad etc...  comment= has
  been added to my local master attribute list as an official attribute.

  -Ales
]

From: Theo Markettos <theo@markettos.org.uk>
-- Cut here --

I've been thinking about our design process at work, and I've come up with a    
few more attributes that might come in handy so thought I'd bounce them off     
the list in case people were interested...                                      
                                                                                
Too often I've picked up a schematic drawn 15 years ago by someone else, and
the reason for component choices have been forgotten.  It would be quite
handy to include some constraints that could appear on the BOM, eg:

value=100nF 100V                                                                
value_comment=decoupling; C not critical; V>70V

value=23R7 0.1% 15ppm
value_comment=R405:R419 must be 17:3; tempco must be 20ppm or better            

Also on the BOM, it would be useful to separate the part number from the
type number.  For example, specify different parts and their sources:

value=4001

manufacturer1_id=CD4001N
vendor1=BigCo
vendor1_id=123-456

manufacturer2_id=MC14001P
vendor2=Corner Shop
vendor2_id=ABC123

value_comment=Don't use HEF4001N

I haven't had a chance to use gEDA in anger yet, but a simple BOM as (for
example) Eagle outputs is often too simplistic - for example a 'value' might
be 'RJ45 socket' and the 'part number' might be 'Molex 12345'.  It's not
particularly helpful to list the part number on the schematic, but the value
isn't always useful when trying to buy components or build the board.

Finally it's useful to be able to list additional parts in the BOM that
don't appear in the schematic.  For example heatsinks, screening cans and so
on that perhaps are something the engineer needs to choose, but don't come
into a traditional BOM.

I'm a bit behind the times as far as current versions of gEDA, so feel free
to tell me these have already been thought about, or are silly ideas :-)

Cheers,
Theo

---- 
Theo Markettos                 theo@markettos.org.uk
Liphook, Hampshire, UK         theom@chiark.greenend.org.uk
                               http://www.markettos.org.uk/