Re: gEDA-user: blue sky ideas - written down finally

[Dave N6NZ <n6nz@xxxxxxxx>]

On Dec 27, 2009, at 6:12 PM, gene glick wrote:

> DJ Delorie wrote:
> 
>> 
>> I'm not exactly sure what's best here, but I know it doesn't belong in
>> the *gate*.  My idea is to have a table object that shows up in the
>> schematic, like in a corner or something, that lists all the power
>> pins and what nets they connect to.  I've seen other schematics with
>> this, it seemed much cleaner than what we do.
> 
> I think you are advocating the logical view schematic (as opposed to a 
> physical view).  BTW, John Doty does this for his connectors - as I recall.
> 
> A schematic represents different things to different people:
> The technician likes the symbols to closely resemble the physical parts. 
>  It makes working on the board easier since he doesn't need data sheets 
> in addition to the schematic.

Physical schematics don't scale.  Only logical schematics scale.  The "tech", actually anybody that comes in contact with the physical hardware, needs pin/card/chassis information to navigate the hardware.  That's why back-annotation of layout information is extremely important.  But a physical schematic of over a few sheets is unreadable.  Nobody can make sense of that.

By 'scale' consider that in the 1980's I worked on a CPU where for the bring-up floor we had of the luxury of two complete sets of schematics printed out on paper.  Each set of schematics was collected into a couple of dozen 3 inch thick binders, which lived in rolling carts.  Good, automated, back-annotation of physical and cross-reference information is the only thing that made dealing with that mass of data practical.  Mostly, I remember chasing things down with microfische versions of the schematics -- paper print outs were just too cumbersome to deal with.  When sitting at a 'fische reader, Xref again is indispensable.  And it has to be automated, there isn't enough man-power in the universe to keep it up to date for a design of any meaningful size.

After than, CPU's got too big to ever print the entire set of schematics on paper again.

Anybody that wants physical schematics has never worked on anything larger than a homework assignment.

In general, gEDA hasn't faced up to its scalability issues.  Which is OK for most current gEDA users, including me.  But scalability is a necessary in the long term.  Slot/pin mapping is a necessary precursor to scalability.  Likewise, a live connection to the company parts database is necessary for a modern schematic editing package.  There's a few other issues in the way of scalability, but I'll get off my soapbox and avoid splitting the thread into a discussion of those issues, too.

-dave




_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user