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Why I Prefer to Create My Own PCB Symbols

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dadeus
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Re: Paper models?
dadeus   6/5/2014 8:16:30 AM
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We use DxDesigner which allows sheet numbers to be entered as attributes.  This has the benefit that it can be updated automatically (should updates require insertion of new sheets) and that it can also be used with off sheet connector icons to add the reference link mentioned in the article.  Although it won't add the alphanumeric block reference, it will add the sheet number(s).  It also allows large fpga parts to be split among banks so we can break the symbols down to whatever size lends itself to better schematics. 

mhrackin
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Re: Paper models?
mhrackin   6/4/2014 8:10:33 PM
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@dougwithau:

 

Sorry I can't help with any recommendations.  I haven't touched any CAD SW for 5+years.  Last tools I used were old Mentor Graphics Boardstation suite AFAIR.  We had done a lot of customizing and adding scripts to take care of much of the "dogwork."

Douglas.Butler
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Re: Paper models?
Douglas.Butler   6/4/2014 7:23:35 PM
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On complex parts like processors where each pin has multiple functions I always edit the pin names to create custom symbols showing the pin functions as I am using them in this instance.  If it means I have two diferent symbols for the same part used twice on the same board or sheet then so be it.  Some of my favorite chjips may have half a dozen symbols in my library for the different ways I use them.

Rick.Smith_#4
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Re: Paper models?
Rick.Smith_#4   6/4/2014 6:37:20 PM
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Sheets still have validity.  Especially if you work for a company that is "paper based."  I work for a medical company where our documentation control system is paper based (the only official copy per FDA rules is the one stored by document cotrol and the official copies are copied from that original and stamped "copy").

My microcontroller board schematic has 41 pages.  The first is the revision and other information.  The second page is the high level hierarchical "function" blocks and interconnections with the page numbers included in each block for that circuit block to act as a road map to get to a particular area of the circuit for troubleshooting.

I really could not imagine having it on one "sheet" or mini blocks with only net names sticking out with no real indication of circuit flow.

 

dougwithau
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Re: Paper models?
dougwithau   6/4/2014 6:07:38 PM
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@mhrackin

I am not arguing that you can not do a good schematic with existing tools. You can definately setup blocks that jump to the correct sheets, name every net, use directed off sheet connectors, and the correct map locators for every off sheet pin (A-5, or D-3, I always called them battship coordinates).

The tools don't seem to help with all that. Right click, properties, type in the net name. Same names are connected. Does the case matter?

I have seen notes tied to a circle for PCIe matched pairs. Is that something that comes through the netlist into the PCB package? From the Adobe PDF file, I dunno.

I am just searching for the better mousetrap.

Roba66
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Altium and Other GUIs
Roba66   6/4/2014 5:53:53 PM
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I use Altium and I agree it is a pain to manage symbols and libraries. The most productive schematic symbol library tool I had was early Orcad where the library was a text file and a new part could be added in seconds. Now we seem to have to use GUIs for everything, which is not productive from my user perspective. (a GUI cannot be automated for one thing)

In Circuitmaker the footprints were a lot easier to manage because there was a fairly complete footprint library which could be matched up with components. Altium seems to provide a lot of libraries and I spend a lot of time searching for things, then give up and design my own footprints. When I do find footprints from different vendors they often have different VIA sizes to complicate the drill files, so I have to change those. 

One further gripe about Altium, the layer controls for PADs in components is very awkward and time consuming, the component GUI works differently than the layout GUI.

I generate a lot of Gerber level patterns, typically a couple layers of antennas and such, that is another reason I would like a textual interface, there is no way I could generate such patterns in the component GUI it would take years.

 

mhrackin
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Re: Paper models?
mhrackin   6/4/2014 5:37:57 PM
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As a high-level systems architect, I am a firm believer in the utility of CAD tools that include hierarchical capability.  Multi-level hierarchy would be even better.   That Page 1 is the top-level image of the entire product to me, and it would include all of the abstact blocks of the design, including COMPLETE definition of all interconnects, both internal and external.  Obviously, bidirectional update (forward and backward annotation) would keep things correct and synchronized throughout the design implementation phase.  Pages are just a convenient way to keep "score" of what's what and where.  My practice has been almost forever to name EVERY net using a standardized notation scheme.  That's especially important for e.g. analog, digital, power, and safety grounds!

Many of my designs had MANY pages, of such size and detail that "hard copies" were readable only on E or larger sheets!  However, "page 1" was always the definitive overview of the total system, and thus signal flows, etc. were very clear on one sheet.

Navelpluis
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Re: why create a schematic
Navelpluis   6/3/2014 4:12:00 PM
@ tb100

Hear say hear say !! 

I agree more with you than my brains can cope ;-)

Seems that I am old-school, just want to make great schematics for the whole process to be easier, and that counts even for myself. Part of the crativity process for me is to forget things within 3 months.... (or call it limitation in intelligence ;-) Good schematics help a lot.

My career after polytechnical school started with PCAD under DOS as well. The same route, except for the Altium part. Here I was lost, I just could not work with it. And now under Chinese government, trying to get your designs "into *their* cloud" makes me shivver, no way we are ever going that route. 

So I am still using PCAD 2006, bought Cadence, but did not find the time to go and use it properly. Cadence tells me to do the whole route again, all symbols and shapes pass my hand.

Lots of people have no clue what this does for an engineer, switching between CAD products. OK, if you do it the whole day it certainly will be easier, but CAD is only 30% of my time, the rest is hard core engineering.

So cheers for the writer of this article. Let me advise to the CAD companies to read this article carefully: I said this many times before: Don't be just a money maker, but enable people to make wonderful things with your software. Look at old stuff like PCAD and add the new high speed stuff to it, that's what I basically think...

 

dougwithau
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Schematic sharing
dougwithau   6/3/2014 3:44:14 PM
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This is a fun debate, keep up the arguments. 

How many people do you share the schematic with?

The tools all make entering and building a schematic a one person job. They come from the days when sharing just did not make sense.

There are some online efforts, but they seem to be recreating the paper model of sheets and symbols.

The schematic needs to go to the board designers, the fab house (yes it should, not just a net list), technicians, the purchasing and parts procurement people, contractors, and vendors. I have been all of those people, sometimes all at once. Is emailing around a PDF file the best we can do?

Do you have concerns about sharing or doing a schematic online?

dougwithau
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Re: Paper models?
dougwithau   6/3/2014 3:39:34 PM
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Betajet,

If I edit the pin names then one of two bad things just happened.

Either, the symbol in the library was just changed to my custom configuration. The information was lost, or must be recreated if that symbol is ever used again.

OR

The symbol was copied, then modified. Now I have done a bunch of work, for a one off symbol, and I have two almost but not quite duplicate parts in the library.

Again, I say Yuck!

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