Groups of Devices

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.