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KevL
United Kingdom
78 Posts |
 Posted - 06 Aug 2010 : 18:47:50
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We have been developing a set of standard libs for some time.
These have been created from a number of sources including Eagle Libs, EZPC IPC libs, EZPC standard libs.
The aim is to produce our own carefully maintained libs which can be trusted and used by a number of engineers at our site.
We have arranged the schematic libs to have value fields which give enough info for the component placed on schematics to be completely identified for schematic review. By using some hand crafted VisualBasic can generate component cost reports and an order for all of the components in a design by pressing a few buttons in EZPC to produce a parts list and then reading the parts list into a liitle excell app. This excell app. contains all of our component data and matches up the items on the parts list report and creates a new report with Farnell/ RS etc order nos, prices etc.
This function works really well.
Occasionally we have trouble with our footprints and I think this is because even though we have phDs and have been designing stuff for years we aren't quite clever enough to get our heads round EZPC tech files. :).
We have tried to standardize on a set of layers which are common to all of our footprints. In retrospect this may be a tad too complex but we didn't know any better.
For our footprints we have the following layers.
Top Silk screen - silk screen
Top mech drawing layer - a mechanical outline showing true extent of component (used for producing assy drawings, DXF and IDF output)
Top footprint Courtyard - This was present in the IPC spec and becuase we had the info in the IPC libs we were lothed to throw it away - even though we dont really use it
Top Paste mask
Top Solder resist
Top copper
And we also have the same layers on the bottom of the PCB stack for our libs though in the vast majority of parts the bottom layers are empty in the libs.
We put an R symbol on the top silk and top mech layer so that we get refdes on top silk and on our mech drawing layer. Sometimes there is no space to have refdes showing on top silk so in these cases we can still produce a drawing with the refdes shown on the mech layer for assy/documentation.
We seen a number of problems with this setup - probably because it is more complicated than is usual????
One of the problems is that we have some primitives present in components which are invisible when editing the footprint - even when all layers are shown but produce unwanted text strings when placed on the PCB. It is as if some primitives have become orphaned inside the components. I can tell they are there by looking in the text styles in the component and seeing text styles as being present but I cant delete them becausse I cant see them.
Today I spent some time trying to sort this out.
It occurs to me that I think I can see how this might have happened. I even have an inkling who did it (twas not I) - but I suppose I cant really blame him as no warning was issued by the package.
If one opens the lib manager and displays all PCB footprint libs and then selects all components then it is possible by hitting tech files button to select NONE as the PCB tech file.
Hitting apply then resets all the layers down to the very few that EZPC libs usually contain - top silk, top copper and one or two others I cant remember which. So if a PCB footprint is now edited then only a few layers are shown. Presumably the rest of the info is still in the libs but it is now invisible as it is on non existent layers.
Now if one again selects all footprints and loads my proper tech file then how does the library manager work out how to remap my layers (maybe a too complex layer setup) to the few layers which are visible using the technology = NONE setting. Is there a way of forcing the libs to reveal invisible primitives - invisible because the layer they are on is not defined in the tech file?
I suspect this is the cause of some of my footprint issues.
This has taken us quite a while to work out and I'm sure it is a problem I could have fixed in minutes if the libs had an ascii out and back in again function. But they don't.
Anyone had to deal with this sort of issue in the past?
Kev
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Edited by - KevL on 28 Nov 2010 17:44:28 |
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KevL
United Kingdom
78 Posts |
Posted - 19 Aug 2010 : 12:43:19
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Oh well 50 views and no advice.
Maybe we folk at my co. do not lack intellect. Tech Files , styles etc in the context of PCB lib files really are not straight forward.
K
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KevL
United Kingdom
78 Posts |
Posted - 28 Nov 2010 : 17:32:09
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110 views
really no ideas how this stuff hangs together? |
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TonyS
USA
16 Posts |
Posted - 07 Dec 2010 : 16:57:16
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KevL,
I too would like a detailed overview of how Design Technology / Technology Files impact / affect components, schematics, and layouts. I already have found that Design Technology settings on schematic symbols is volatile. Maybe the overall explanation is part of the EPC documentation, but I haven't run across it yet.
I don't know if it will help or not, but when I find a "mystery" text or line style on a schematic / symbol (I don't do pcb layouts - yet!), I temporarily increase the "Width" of the mystery primitive so that I can easily locate it. |
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KevL
United Kingdom
78 Posts |
Posted - 09 Dec 2010 : 21:29:09
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quote:
I already have found that Design Technology settings on schematic symbols is volatile.
By volatile I suspect you mean changes do not stay changed. When lib items are opened they occasionally seem to have changed by themselves.
I think that the way tech files relate to library items is buggy. I do not believe it works as intended.
Maybe as the library format has changed over the years - as new primitives and functionality have been added - then bugs or unintended consequences have resulted.
I have read and re-read all the docs re this. It really is not clear how this stuff actually is supposed to work.
I think the below is a fair question
quote:
If one opens the lib manager and displays all PCB footprint libs and then selects all components then it is possible by hitting tech files button to select NONE as the PCB tech file.
Hitting apply then resets all the layers down to the very few that EZPC libs usually contain - top silk, top copper and one or two others I cant remember which. So if a PCB footprint is now edited then only a few layers are shown. Presumably the rest of the info is still in the libs but it is now invisible as it is on non existent layers.
Now if one again selects all footprints and loads my proper tech file then how does the library manager work out how to remap my layers (maybe a too complex layer setup) to the few layers which are visible using the technology = NONE setting. Is there a way of forcing the libs to reveal invisible primitives - invisible because the layer they are on is not defined in the tech file?
Have to say info re this from the forum has not overwhelmed.
Moons ago I suggested a means whereby libraries could be cleaned of spurious styles, be made consistent and have a standard tech file applied to them - here.
http://www.numberone.com/forum/topic.asp?TOPIC_ID=492
I had to turn off forum notifications for replies to that thread. I feared that there would be insufficient disk space on my server to accommodate reply notification emails.
The previous sentence contains a non-truth. :-)
Kev
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Peter Johnson
United Kingdom
498 Posts |
Posted - 22 Feb 2011 : 10:02:59
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Whoops. sorry, missed this one.
OK. Primitives 'know' which layer they are supposed to be on. They don't care about the layer name, unless there's ambiguity. Principally they use a combination of layer type and layer side. As only one layer using a particular layer type is allowed on [Top] and [bottom] layers, this is often enough. It's only with inner layers that the name may be necessary to resolve the actual layer.
The technology file used for pcb symbol editing is the one shown if you go to [File], [New] and select 'PCB Symbol'. It's faster to check there if you don't have the library manager open, otherwise you can use the [Tech File] button.
If you've edited a symbol with a reduced layer line-up, the 'stuck' prmitives should remember their defaults and behave correctly if you reopen with a tech file which supports them. The program normally hides anything it can't match to a layer. (Perhaps a case for a 'Show All' function?)
Does that fill in the blanks, or do you still have problems? |
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AndyB
United Kingdom
208 Posts |
Posted - 06 Dec 2011 : 16:04:13
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I would like this to be resolved as I have had problems with tech files.
I have footprints that have lost their link as mentioned by KevL and only when saving/exiting does it ask if I would like to update the tech file.
Doing so does not always update it. |
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Topic |
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How tech files work with PCB footprints