Re: gEDA-user: "mm garbage", cannot repro

[Stefan Salewski <mail@xxxxxxxxxxxx>]

Am Donnerstag, den 20.11.2008, 00:55 -0500 schrieb DJ Delorie:
> 
> I can.  Set a 0.25mm grid and draw a bunch of lines that *look* like
> plain 45 lines (i.e. no obvious corner, like you'd often get with _/,
> and don't use X).  About one in four will produce a 1/100 mil line to
> compensate for the grid rounding.
> 

Thank you all for verification and discussion of this problem.

I have done some testing by simulating a 0.25mm grid my a mil grid and
command setvalue(grid, 9.84, mil).

I think this works better than real 0.25mm grid.
I tested with a part with 0.5mm pitch (QFP208_28).
If "Crosshair snaps to pins and pads" is turned off all works perfect.
As supposed, when  "Crosshair snaps to pins and pads" is turned on, then
these short lines are  generated when pins are connected to grid points.

If pcb program would map each pin internally to nearest 0.01mil based
grid point and display in coordinate window "0,25mm" instead of "9.8mil"
all may be perfect?

> 1 in = 25.399999999972 mm not exactly 25.4 but close enough for
>layout work if you use high enough precision.

Of course, if indeed "1 in = 25.399999999972 mm" should be true we can
always define for our pcb world "1 in = 25.4 mm". The result may be that
a fabricated boards is a few nanometers to large or too small -- no
problem.

Best wishes,

Stefan Salewski




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