At 03:58 PM 6/29/01 +1000, Ian Wilson wrote:
I will throw back at a designer a sch that does not show the correct
footprints as used on the PCB. Parts lists are prepared from Sch no PCB (by
us at least). Would you like to be responsible for an incorrect footprint
being purchased. I see no excuse for not synching completely the Sch and
PCB before initial release of the PCB.
Okay, here is an excuse: the designer does not necessarily have control
over the schematic. This is not uncommon.
In a consistent internal company environment, it is obviously better that
schematics be reconciled completely with the PCB.
Another excuse is that the board must go out the door, and the designer is
yanked to another project, but, with the synchronizer, this is less and
less excusable.
>>Bottom line: if boards have been designed in an undisciplined
>>environment, and have been fabbed and work properly, don't monkey with
>>the assigned footprints unless you want to review the whole design. And
>>using the present update tools would be too crude.
>
>Why? They would show a discrepancy between Sch and PCB and this would be
>valuable. Then Matthew would need to investigate why there is a
>discrepancy and make a judgement on if and how to fix. The fix may simply
>be a text file stored with the PCB and Sch pointing out that the
>discrepancies exist - to warn future suckers.
Sure. By "monkeying" with the assigned footprints I mean changing them
without being sure whether the PCB or schematic are more correct. Making a
text file of deviations for future designers is certainly a good idea.
Resolving all these deviations may be more trouble than it is worth; it
depends....
>>Instead, a partial check could be done by making a PCB project library,
>>back-updating the footprint names to the schematic, and then using that
>>library and the schematic to check assignments. This would detect, for
>>example, that the schematic usage of, say, 0805 and 1206 packages was
>>consistent with the PCB.
>
>Nah... let the Update Sch macro report show any footprint discrepancies -
>one can even save the report for detailed analysis.
Problem is that if the schematic is massively unsynchronized re footprints,
as easily happens with designers who make footprints and place them on the
fly without going back through schematic, that macro report will be so full
of changes that it will make little sense. By making a project library,
which was the core of the suggestion, one at least has a consistent set of
footprints that actually match what is on the board. The basic assumption
here is that, since these boards were fabbed, they were good. That is not
always true, of course. Then by taking that back to the schematic, the
footprint fields in the schematic -- which are quite likely to be incorrect
if left alone -- will be updated to reflect the PCB. BOM's from the
"before" and "after" schematics could then be compared. But I did not
express this correctly....
>I assume since I seem to be going against most of what you have to say
>that I have mis-understood the fundamental point you are making. In
>essence, you seem to be saying that the synchroniser is not satisfactory
>for Matthew's task. I disagree, I think the Update Sch process is
>possibly going to be the easiest and quickest method of comparing Sch
>against PCB - particularly if the original boards where created using the
>synchroniser and so have the magical hidden handles allocated.
There is a high probability that the boards were *not* created using the
Synchronizer....
Alternatives to the use of the Synchronizer were suggested because
sometimes the Synchronizer seems to take forever to come back with a
report. But let me repeat what I said at the very beginning of my comment
in this thread. I do not know which process will be the fastest.
And getting 100 schematics cleaned up is going to be a big task no matter
how you slice it. Yes, it would have been much better if they had been
cleaned up immediately and everything rectified before the boards when to fab.
[EMAIL PROTECTED]
Abdulrahman Lomax
P.O. Box 690
El Verano, CA 95433
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