Mail Archives: geda-user/2012/12/13/23:05:15
On Fri, 14 Dec 2012, Markus Hitter wrote:
> Possible solution: instead of drawing tracks, board design starts with rat
> lines. Like we currently have them. Then, these rat lines are - sort of -
> pinned down to become, or being morphed into tracks. Perhaps with a tool
> similar to how paths are edited in drawing applications. Add vertices, drag
> these vertices, join them to forks, and so on, until the board is done. But
> never disconnect a track in this process.
>
This is one of the many ways you could build your tracks. In some cases
this is not the most efficient way.
Imagine a large city with a river cutting it in two halves. You need to
plan your route from one end of the city to the other end, crossing the
river. There are much less bridges over the river than streets on each
side, and you sure need to cross the river which means you will walk one
of the bridges. In cases like this it often simplifies the situation if
you can pick one of the bridges and then route to/from the bridge on the
sides.
In PCB I very often see a bottleneck, sort of a bridge over an obstacle
cutting accrsoss my board, and I know i will be routing multiple nets over
that narrow bridge. Often I prepare this while I am working on the
obstacle and the bridge, for example placing a 1206 resistor and two,
thinner-than-normal traces in between the pads, unconnected. For toner
transfer this helps.
An other cases is when I have 2 parallel signal traces, goung around the
whole board. I route them mostly as you suggest, building at the end of
the current trace. However, when I reach the final destination, I figure
it'd be easier to swap them (possible with or without back annotation of
the change, for example at the last two pins of a SIP/DIP). In the latter
case I first disconnect both long traces from the startpoint, connect
them in reverse and the crossing rats are solved on the other end.
> This way, tracks are never disconnected from a net. Finding a short becomes
> trivial. Probably a number of other tasks, like track length measurement, too.
Yup, if you choose to live with that restriction. If you don't, and want
to delete objects from the middle of a trace and rewire things, it would
break. My personal opinion, as a PCB user, is that it'd be a inconvinient
feature considering the methods I use for designing my boards.
On the other hand, when you connect two tagged nets, it could show the
short at the point they are connected; this very same feature can be
produced with the historic approach (bisecting the undo buffer). Tagging
does not solve the same problem as the historic approach can't: what if
the netlist changes?
Regards,
Tibor
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