Question about schematic design library parts

Discussion in 'General Electronics Chat' started by osx-addict, Jul 27, 2012.

  1. osx-addict

    Thread Starter Member

    Feb 9, 2012
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    Hi all.. So in playing around with various schematic capture tools, I'm wondering how you all deal with library parts that you create that have tons of overloaded pins such as those found on 28 pin PIC32 parts or some if it's cousins -- where some of these pins have 4-6 things on each pin.. If I label each pin with ALL of the names I get a part on my schematic that is just plain HUGE taking up a lot of space -- that wouldn't be a big problem IF I owned these products but many of the free/trial versions don't allow more than one sheet so one part consuming a large piece of the sheet is not workable..

    In posing this question to one company their response was this :

    Is this what any of you do or is there some other way I'm not aware of -- or do you just live with these REALLY wide parts?

    PS I realize the other option is to break the library part into many pieces (e.g. port A, Port B, Power,etc) but I'd really prefer a single part in this case.

    At this point I'm tempted to just add a small table somewhere on the drawing to map pin #'s to functionality.. or just leave it off and force you to read the spec sheet.. That gives me a nice small schematic part with nothing but pin #'s..
     
  2. JohnInTX

    Moderator

    Jun 26, 2012
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    In Eagle, I identify the major function of a pin (Vdd, RC7 etc) and the 1 or 2 most likely alternate functions if they fit. But I try to keep the symbol size down to something manageable. If you use an alternate function for the pin, name the net accordingly and place a label on the wire near the processor.

    Rather than a table on the drawing, I use an Excel sheet made up for the specific processor. Ordered by pin number, I have a set of columns on the left that identify the pin type (analog, digital etc), any specific limitations (output only, low current drive, IRQ etc) and alternate functions (CCP etc). I highlight/dim any pins that are already assigned (ICSP, debug etc) then fill in the rest. I use the sheet as a guide to generate the I/O definition file(s) and for documentation.
     
    Last edited: Jul 27, 2012
    osx-addict likes this.
  3. osx-addict

    Thread Starter Member

    Feb 9, 2012
    122
    9
    Thanks John for the tip -- I like the idea of the spreadsheet.. I've already got a spreadsheet for tracking parts pricing & where to get specific parts from, so that is a nice addition!
     
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,387
    1,605
    I use Kicad. My method is to construct a custom library used (and stored) just for that project. Then I am free to modify any and all components as I perfer them, and since they are local to a particular project I am free to change them again on another project.

    For PICs, I prefer to name the pin with just the function I am using. I'll also shift pins to group for functionality and not where they lead out physically .
     
  5. osx-addict

    Thread Starter Member

    Feb 9, 2012
    122
    9
    Thanks Ernie.. Also good tips to know.. Hope to have some time to get back at it soon.. Been spending my free time cleaning up a rental house hence my other questions about sprinkler wiring et-al.... Ugg!
     
  6. osx-addict

    Thread Starter Member

    Feb 9, 2012
    122
    9
    John.. Would it be possible to get a copy of one of your spreadsheets to get a better idea of how you lay things out? I don't care what PIC part it's for -- I'll only use it as a template of sorts to start tailoring it for my PIC32MX150F128B part I've selected.. Your spreadsheet doesn't even need to be complete -- probably only a handful of rows would be sufficient to give me enough info to fill it out for my part.. If you could do that, that would be awesome -- if not, I understand as well!

    Edit : Nevermind.. I think I found one I can work with.. I'll post it here, once I'm done editing it, for reference in the off chance someone else might find it of interest..
     
    Last edited: Aug 2, 2012
  7. osx-addict

    Thread Starter Member

    Feb 9, 2012
    122
    9
    Ok.. Here's the spreadsheet I promised.. Perhaps someone will find it usable.
     
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