Re: gEDA-user: pick and place ?plugin?footprints.c? for

[Dan McMahill <dan@xxxxxxxxxxxx>]

Dave N6NZ wrote:
> 
> 
> Dan McMahill wrote:
>> Dave N6NZ wrote:
>>> What are the barriers to other angles?
>>
>> Think about a SOIC package for example.  It is fairly easy to decide 
>> what quadrant pin #1 is and once you know that, you're done if you 
>> only allow 90 degree steps.  Now suppose you allow 45 degree steps.  
>> Pin 1 for a SO6 will be in a different 45 degree slice than pin 1 of a 
>> SO16 of the same orientation.  If you want to support arbitrary 
>> rotations, you now have to take more steps to estimate what the axis 
>> of the part is. There could be some metrics like "look for rows of 
>> pins that fall on a line" but that will clearly fail for something 
>> that has its pads/pins distributed around a circle.
> 
> OK, I understand the algorithm now.
> 
> But... since most pads are strokes, wouldn't looking at the XY endpoints 
> of any single pad give you the rotation of one axis?  This fails on 
> precisely square pads, of course.  But on any SO or TQFP part, just 
> looking at the end points of pin 1 will tell you rotation.

hmm.  Thats a good idea.  I don't think it quite gets you 100% there 
because if you compare a typical pad on an SO to something like one of 
the larger smt resistors I think the pads are 90 degrees out.  But I do 
think that perhaps combining your idea with the current code might do 
it.  In other words, we figure out what quadrant we're in with the 
current code and then use the angle of the pad to figure out where 
within the quadrant.  What do you think?

Of course with a DIP or other 100% leaded you're sunk but then again 
I'll bet these days almost no one is machine stuffing leaded parts.  If 
they are, they get what they deserve ;)

With regards to square pads, how about this.  Add an extra rule that 
says if you have square pads then look to see if it is a 2 pin 
footprint.  If so, figure out rotation from the line formed between the 
2 pins.  I'll bet this captures most (but of course not all) of the 
square pad cases.

-Dan


_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user