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At 11:39 AM 10/4/01 +1000, Geoff Harland wrote:
>What I was saying previously was that the RS274X standard does not support
>"flashing" thermal relief patterns having just two openings. Given that
>situation, the associated arcs (of these patterns) should (normally) be
>"drawn" instead.

RS-274X has a primitive called a "thermal," yes, and it has four spokes by 
nature. But RS-274X was designed to be *very* flexible, so basically *any* 
shape can be defined as an aperture macro.

When Protel allowed differing numbers of spokes (many programs don't), it 
is rather obvious that no one ever told the people writing the photoplot 
routines. This has been broken, I suspect, for a long time.

Ultimately, I think we should go to defined padstacks, the existing Protel 
pad shapes are one of the major limitations of the program. I would 
definitely use a chamfered rectangle (kind of like an "octagon" should be, 
but not regular and not broken) if Protel supported it. I used the Tango 
"rounded rectangle" all the time. (that's a rectangle with rounded corners).

Yes, padstacks are complicated but if the program automatically generated 
padstacks to match the existing status quo, but then we could lift the hood 
and edit and modify or add to those padstacks, we'd have our cake and full 
stomachs as well, to mix a few metaphors.

So the photoplot routines could simply define a macro where the existing 
basic RS274X shapes won't work, and then flash the macro code. Easy peasy, 
best of both worlds: a drawn shape but compact plot files.

(As an aside, such creatures would make back-conversion from Gerber easier, 
because they would define a connection to the plane just as a thermal 
presently defines such a connection. Drawn thermals are harder to recognise 

Abdulrahman Lomax
Easthampton, Massachusetts USA

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