Re: gEDA-user: How to find which specific part of a PCB is shorted?

[Stephen Ecob <silicon.on.inspiration@xxxxxxxxx>]

> I remember the old Quake maps had to be "sealed", so any loose seam
> would cause problems. Because the map editor doesn't know what you
> meant to be outside/inside, etc, the map editor had a feature to deal
> with this, it would create a line that would start in one area, and
> head to another. All you had to do was follow the line.
>
> A similar solution in PCB would be neat. if VCC and GND are shorted,
> pick a random GND pin and a random VCC pin. Find a path between them
> and show it as a orange dotted line. This could later be extended to
> find either the shortest orange dotted line, or the point on the board
> where several such lines meet.

Yes, plenty of possible algorithms - the one that I though of was:

For each element in the set of elements in the two shorted nets
{
  Temporarily disable this element (ie consider it an open circuit)
  If (the two nets are still shorted)
  {
    re-enable this element;
    continue;
  }
  re-enable this element;
  Visually highlight this element;
  Alert user("This is the offending element");
}

The algorithm fails if the short consists of parallel shorting
elements - but the very common case is just a single fault, very often
that via with extra thermals on a wrong layer.

If only I had time for more than pseudo code at the moment!

Stephen Ecob
Silicon On Inspiration
Sydney Australia
www.sioi.com.au
$39 Spartan 6 board with 32MB DDR DRAM ?
http://www.sioi.com.au/shop/product_info.php/products_id/47


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