At 03:05 PM 2/22/2002 +1200, Steve Baldwin wrote:

> > If anyone is interested, it is my belief that an "off-line" inverting
> > utility could be created
>Although not the Holy Grail, I think an "off-line" utility would be a
>sufficiently useful tool for the majority of my applications. I still use
>Ian's viewer and find it useful for checking without going through a
>Gerber/Print cycle.
>I can think of three distinct situations where I would use it
>(generally on SMT through wave boards)
>1) After placement of top side, through hole parts. Arrange SMT
>stuff on the other side.
>2) Arranging Ref Des and other text to look right from both sides.
>3) Producing a placement file / drawing for the SMT parts. As far as
>the SMT guy is concerned, that is the top side of the board.

None of these justify actual PCB inversion.

Display inversion would be a convenience if we had it, Protel should 
provide that in Options/Display. This would be *relatively* simple to 
program, because it would have no effect on the PCB database.

We can already mirror prints and plots, so fab and assembly considerations 
do not need actual PCB inversion, where top becomes bottom, etc. That's a 
fairly large "etc."

But an inversion tool *would* be valuable with design re-use. I might want 
to take a piece of an existing design and merge it with pieces of other 
designs and new stuff. I might need to invert the layers for some of the 
pieces, this would not be uncommon.

What would do it would be a limited inversion tool that would swap layers 
and mirror. Layer swapping would be according to a conversion map that 
would default to simple reverse order. There might be aspects of the PCB 
file that would not need inversion, Mr. Wilson and Mr. Harland have worked 
intensively on the problem and would know more about the difficulties which 
could be encountered.

As to display inversion, it should be simple enough to accomplish and 
useful enough to be worth doing. But most of us have learned to work in 
mirror, which is why we aren't screaming for this feature.

If one wants a quick view, the solution suggested to have a print preview 
window open and refresh it when needed would work, but could be 
time-consuming given how long the gears turn in the Print Preview. 
CAMtastic, however, loads gerber files quickly and has the advantage of 
giving a truly WYSIWIG display. I've never felt it necessary to do this, 
however; while working on a bottom legend, it is easy enough to rotate the 
lettering according to one's scheme, and the occasional stray overlooked 
designator can be caught with a global edit.

Abdulrahman Lomax
Easthampton, Massachusetts USA

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