Hello,
The issue is that when you're trying to interface to another module (say a
PC104 card or something like that) it is very useful to create a device to
capture that interface. That way it's the same every time. I'm sure
people run into this all the time.
However, when that module has multiple connectors it becomes problematic.
Let's say I have board with 2 0.1"-pitch sockets on it that has a certain
amount of area for a daughter-board. To mate to it, I need the
daughter-board to have the correct size and have 0.1"-pitch headers in the
exact right place. To ensure I get it right every time I create a
footprint that has all the holes needed, a board outline, even some silk
screen. So when I get to my PCB all those things are in the exact right
position relative to each other. I move it as a group and it all stays
together.
However, I also need x-y data for those headers on the daughter-board for
manufacturing. There's no way to get that out of EAGLE. There are
workarounds, and I use them, but it's a kludge and prone to error.
One way is to create the "module" from discrete devices. That works for
the BOM and x-y data but you have to position the connectors and other
features exactly and it's possible to move one relative to another--which
makes the module interface incorrect. You can lock the devices so at least
they won't move but you can't lock holes, silkscreen, dimension layer
features, etc which are also parts of many modules.
And one of my rules is that manufacturing data (BOM's and XY data) should
never be hand-edited--to much room for error. I want the CAD tool to be
able to auto-create this data.
So we need someway of defining a connector within a module. And I'd like
all the regular attributes and everything else that goes with real
devices.
Maybe a composite device with is a sticky group of devices? The gates
(symbols) could be handled like heterogenous parts. On the PCB side you
would essentially make a mini-pcb, positioning connectors, adding silk,
text, ....
The idea is we get the best of both worlds:
1) a BOM and x-y data file that is auto-generated and correct for what is
actually build
2) a footprint that is done once in the library and then reused with
confidence.
Cheers,
James.
--
James Morrison ~~~ Stratford Digital
Specializing in CadSoft EAGLE
Online Sales to North America
Electronic Design Services
EAGLE Enterprise Toolkit
--
Web access to CadSoft support forums at www.eaglecentral.ca. Where the CadSoft EAGLE community meets.
