kicad-developers team mailing list archive

[jp charras <jp.charras@xxxxxxxxxx>]

Le 26/11/2014 21:54, Thiadmer Riemersma a écrit :
> A question (because I am confused): are attributes not exclusive to X2?
> 
> I understand the Gerber specification as: X1 = RS274X = Gerber without
> attributes, and X2 = RS274X + attributes.
> 
> Regards, Thiadmer Riemersma

Yes, X2 = RS274X + attributes

The X2 format define some standard attributes:
- File attributes.
- Aperture attributes.
(There are some other attributes in Gerber Drill Files)

The most important attribute is the file attribute.
There are 3 file attributes.

The most important file attribute is "File Function"
for instance, at the beginning of a Gerber image file of a 2 sided
board, Pcbnew inserts the line:

%TF.FileFunction,Copper,L2,Bot,Signal*%

to identify the back side.

The X1 (or RS274X format) does not have a file function attribute.
However, in X1 files, Ucamco recommends a file function attribute using
a compatible mode.
The syntax is:

G04 #@! TF.FileFunction,Copper,L2,Bot,Signal*

which appears like a comment (G04) for X1 readers, and (for very recent
X1 reader ) is a pseudo comment, in fact a file function attribute.

"G04 #@! " starts a attribute in X1 mode.

In X1 format, Pcbnew adds this pseudo comment, and Gerbview read and
uses it.

-- 
Jean-Pierre CHARRAS