Re: [PROTEL EDA USERS]: Drill Drawing

[Abd ul-Rahman Lomax <marjan@vom.com>]

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At 01:39 AM 9/26/00 -0500, Jon Elson wrote:

>Don't try to look at the .TXT file with a gerber file viewer.

Technically, Mr. Elson is right. But many "gerber" viewers are really more 
general "CAM" viewers, and will view drill files. Certainly GCPrevue does; 
I haven't tried to use CAMtastic for this, but I would not be at all 
surprised to find that, as Mr. Harland reports, it will read drill files.

>Although
>these files are both variants of RS-274D (or X) syntax, the Gerber
>files are generally created with leading zeroes suppressed and no
>decimal points, and the drill files are generally created with TRAILING
>zeroes suppressed, and no decimal points.  For this reason, the files
>will massively corrupt the interpretation of coordinates.

In both cases, gerber and drill, zero suppression, whether or not it is 
leading or trailing is an option. I prefer to generate drill files with 
*no* zero suppression simply because it makes the file very easy to read, 
and drill files are typically quite small, so file size is not an issue.

Leading zero suppression is also easy to read. With files on an inch grid, 
assuming that the files are generated in inches, trailing zero suppression 
can save quite a few characters, making it easier to send the files over a 
narrow pipe.... In either case, any gerber viewer can be set for the 
appropriate zero suppression state for each file. With a good viewer, this 
is done automatically from information in the file header.

By the way, another device for reducing gerber file size is to turn off 
software arcs. This will permit Protel to use the gerber arc command 
instead of drawing many individual segments. The only down side, unless one 
is using an antique plotter, is that someone who is trying to import the 
files into an older CAD program might find it difficult. I only mention 
this because I used to be in that position....

Centering the plots on the film can put objects off grid, and thus the 
savings from trailing zero suppression might not exist. Centering also 
causes the gerber to have a different reference zero than the drill files, 
and for that reason and for others I never allow it.

marjan@vom.com
Abdulrahman Lomax
P.O. Box 690
El Verano, CA 95433



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