At 07:52 AM 12/18/01 -0600, Dave Eloranta wrote:
>It would seem that Protel 9SE and Camtastic must
>share some unit conversion code that has a bug.

I doubt that they share code. I'd be interested to look at the actual 
gerber generated with the arc problem that Mr. Eloranta reported.

I looked on the Knowledge Base and was unable to find any articles relating 
to these problems. But it is not necessarily easy to find such....

To my mind *any* plot errors are mission-critical. I did receive an 
immediate response from Michelle Covington at Protel US support that she 
verified the problem. I did make it easier for her by providing not only a 
cut-down edition of the problem board file, but also the CAM definitions. 
In any case it was nice to get such a prompt response.

There should be only one round-off in the process: plotting to less than 
full precision or different units (or export to database formats of lower 
precision), and round-off should never be truncation but nearest value, 
even preferred.

Conversion of high-precision units to plot at lower resolution could cause 
various kinds of issues. For example, if a fill draw is rounded down in 
sizeand position, gaps could appear in fills unless the fills were 
overlapped; this should receive special attention.

For some reason, fill routines tend to have had, in my experience, 
problems. Tango never did get it completely right, as I recall. And even 
when the fills were right, they tended to have about twice as many 
primitives as necessary, plus they had problems with intersecting outlines.

Protel does not support, as I noted, true rotation of pads through the plot 
process, they are not flashed, but they are drawn, with an aperture which 
we do not control in RS-274X (we might be able to control it if we use an 
aperture table, which has other problems). So we might think we can make a 
sharp corner with a fill, but it actually turns out rounded if the fill is 
other than orthagonal.

Abdulrahman Lomax
Easthampton, Massachusetts USA

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