At 05:34 PM 10/1/2010, you wrote:
Rick Collins wrote: >>If for whatever reason the designer used 2 different footprints for >>the same part occuring >>several times on a board, if the footprints are position/rotation >>inconsisten... > > I have no idea why anyone would do that. Real world example: PhD student Foo designs some super noiseless detector circuit. The measurements turn out a success. Researcher Bar, a long time friend who works on some unrelated project, asks Foo for help to get him started on noiseless detector. PhD Foo gladly provides the schematic and layout. For his project Bar needs to add some minor features to the hardware. Of course, she uses a different local library than Foo ... > Sure the designer can totally screw up a design. I wouldn't call this totally screwed.
If you work on a design and use a different, incompatible library from the original without checking for consistency, yes, the designer totally screwed up.
I really have no idea how things work in the gEDA/PCB world. With FreePCB the library has a default orientation for parts and there is a centroid vector to allow the pin 1 orientation to be set compatibly with the Gerber files. If you use someone else's design you need to verify that their library parts were done correctly or you need to use the same footprints which are a part of the layout and so are available. There is no reason to screw up something as simple as this.
Oh, I almost forgot, NEVER ask a PhD "anything" to design PCBs. What the heck are you thinking???
Rick
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