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New CAD design questions.

Discussion in 'CAD' started by Jamie, Jul 1, 2007.

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  1. Jamie

    Jamie Guest

    I'm building a new Electrical/Electronic type Project CAD program
    that will combine Drawings of several types, Board lay outs with foot
    prints, cabinet lays and drilling templates etc.. a
    This will all be in a single IDE tool with tab pages and properties
    settings etc...
    What I would like to know its this..
    The Library database storage methods..

    Create Symbol/Foot prints database as:

    (1). Binary formats // Faster and more compact.

    (2). Binary formats with optional Script generation.

    (3). Script format all the way. // much slower to process but can be
    manually edited if need be..

    Would like to know what would be the best format ?

    the IDE will also include all the tools to create the symbol library.
  2. qrk

    qrk Guest

    Store it in whatever format works for you. However, being able to
    convert to and from ASCII format is really nice as it allows one to
    create their own library generator, perform scripted editing of the
    libraries (you gotta love SED!), and create many-pin symbols with a
    text editor. Xilinx is one company that supplies ASCII files of FPGA
    pinouts. Allows one to make a 700-pin FPGA schematic symbol in less
    than 20 minutes. GUI tools to generate symbols are fine for a few
    pins, but when the pin count gets into the tens or hundreds, ASCII is
    the way to go.

    Look at the old DOS Orcad tools. Everything was editable in ASCII
    form. Even the intermediate netlist format was ASCII which allows one
    to create their own net list formatter. One guy just recently wrote a
    program that generates thousands of IPC footprints to the old DOS
    Orcad PCB program because Orcad PCB can import ASCII descriptions.

    Your PCB and Schematic files should also be convertable to and from
    ASCII format. I often find myself making changes via a text editor to
    my schematics or creating multichannel schematics by editing ASCII
    representations. It really saves time.

    Don't forget about macros and user definable hot keys.

    If your project is open source, you may be interested in joining up
    with a new project that is looking into creating a schematic and PCB
    program suite. The primary focus is productivity, unlike most of the
    other programs out there. If you're interested, I can send you details
    on joining the group.
  3. Hal Murray

    Hal Murray Guest

    For things like Xilinx, I suggest a 2 step approach.

    One file describes the chip. Which pins are power? Which
    signal pins are input, output, tri-state...

    A second file describes the design and the mapping of signal
    names to pin numbers. Maybe this file has hints about
    how to draw the pictures.
  4. Jamie

    Jamie Guest

    Basically what I am doing is creating what I call an
    inherited database of symbols. these would be the most
    primitive types like circles, boxes etc. that are in a vector
    type so that size can be adjusted when applied to another
    symbol design etc.. the final end will be a vector type
    graphic to be used
    the final graphic will have magnetic connection points to
    make it easy for you to lay it out. each project will be
    storing the drawings in a vector type system that encompasses the
    symbol drawings and the node map to draw on the display..
    I suppose I could dump this out in an ASCII format also.
    By including all of the required symbol data in a section of
    the files, one could open this schematic for example and be able
    to view even if they don't have the symbols on board but could
    grab a copy of the symbol and add it to their own lib.

    It will make for a larger set of schematic files how ever, the
    danger lye's in one day you may want to open the file that may have
    used older foot prints that you no longer have maybe due to a crash
    or what ever.
    Also a simple viewer could be created just for viewing much like the
    PDF system..
  5. Marra

    Marra Guest

    I have written a PCB CAD program over the last 12 years and I opted
    for the binary approach.
    This allows the data to be more compact than scripting.
    It was originally written for DOS hence the compact data system.

    Having said that there is no reason why a converter could not be
    written to edit the binary data.

    As for editing I just wrote a good symbol editor that was very easy
    for the user.
    Instead of just allowing the user to plonk pads everywhere I asked for
    some parameters upfront and got the software to place everything. You
    still had the option to edit it afterwards if need be.
  6. qrk

    qrk Guest

    Embedding the parts in the schematic file is a good thing as it makes
    the project portable and self-archivable.

    For the PCB program, it's also a good idea to have a DXF import/export
    function. This allows you to draw up complex footprint or board
    outlines in a drawing CAD package then import to the PCB program.
  7. Jim Thompson

    Jim Thompson Guest


    The old original MicroSim (PSpice) Schematics is all ASCII and has an
    archiving method that pulls only those symbols used in that particular

    Which is a good deal... I literally have THOUSANDS of home-brew

    ...Jim Thompson
  8. Joel Kolstad

    Joel Kolstad Guest

    Do it this way using, say, XML. Sure, it's slower than binary, but on a
    modern PC in all likelihood you'll still be waiting on the hard drive for the
    actual data, so there probably won't be any difference in *actual* execution
    time based on the binary/ASCII choice.
  9. Joel Kolstad

    Joel Kolstad Guest

    12 years ago, this made plenty of sense. Today, with 500GB hard drives
    selling for $100 and file systems that support on-the-fly compression, I think
    the ASCII/XML approach makes much more sense.
    The usual problem here is that if you have a corrupted library file, most
    converters use the exact same code to read the library as the regular program
    does, and therefore will die a horrible death as well, preventing a (manual)
  10. Hal Murray

    Hal Murray Guest

    Embedding the parts in the schematic file is a good thing as it makes
    The downside is that it's harder to fix a bug in a library part
    and or share library info with other designs.

    The original question was ascii or binary. You tossed in another
    interesting consideration: archiving.

    My preference is lots of small tools rather than one big GUI mess.
    A major advantage is that I can often do something that the
    one-big-package doesn't do.

    What I really want is something like make and the tools to generate
    a makefile so I can easily be sure that I have done all the steps
    I need to do when making gerbers and archiving everything.

    Lots of small tools generally work better with ascii than binary.

    If the performance hit is serious, I'm happy using binary
    files as long as there is a simple way to translate beetween
    them. I'd be surprised if that happens at the board layout
    level - maybe for large boards.
  11. Bob Woodward

    Bob Woodward Guest

    Another good thing is that a schematic file can be used as library.
    Removing wires, Sorting the parts, write their names alongside and
    print it for easy lookup. Same for board-lay out.

    For me, even with available libs containing thousands of parts I need
    to edit a part right in the first project.

  12. qrk

    qrk Guest

    On Tue, 03 Jul 2007 00:00:58 -0500,
    This is one of the reasons I still use the old DOS Orcad schematic
    tool, SDT. Over the years, people have written apps and drivers to
    modernize aspects of SDT. I cringe when I see customers fighting with
    With Layout/GerbTool, I have written a macro for GerbTool that moves
    the fab files to other directories. Sure reduces the headache of
    moving those files by hand.
  13. Marra

    Marra Guest

    Why would the file ever get corrupted?
    I have yet since I wrote the first version in 1990 to get a corrupt
    library file !
    It shouldnt happen unless there are bugs in the software or someone is
    extremely stupid like switching the PC off by mains instead of logging

    The binary method means the data can be held in simple arrays in
    memory instead of on the hard disc, making reading and writing very
    very fast. Even with modest amounts of memory massive pin loadings can
    be used with binary.
    I also fit strings exactly into memory without allocating something
    silly like 64K to a string each time. It makes for very careful
    programming but I find if I do make a mistake it goes horribly wrong
    which is better than missing something.

    PC's do have massive storage and power now but I still find .NET V3
    graphics slow even on a dual core PC.
    Having moved on to ORCAS it is even worse still.
    It doesnt matter how much power PC's have it is never enough to keep
    up with the demands of the latest OS.

    I also embed the library parts used into the schematic.
  14. Joel Kolstad

    Joel Kolstad Guest

    Most likely reason: Bugs in the software. I've used various EDA tools over
    the years, and I can specifically recall all of ORCAD, PCAD, Protel, and
    Pulsonix corrupting files at some point. (ORCAD Capture is bad enough that I
    can *almost* get it to do so consistently... not that I think being able to
    demonstrate such a problem would actually cause Cadence to *fix* it, of
    Yes, but your software is nowhere near as sophisticated as most contemporary
    EDA tools. More sophistication unfortunately often correlates with more
    Most string libraries today use aliasing/copy on write to reduce memory
    requirements along with some heuristical approach to memory allocation (e.g.,
    start all strings at, say, 16 bytes, grow the memory allocated to them by a
    factor of 2 whenever they hit the current size limit) to keep performance up.
    I'd be surprised if any commercial products were so bad as to allocate 64K to
    each and every string.
    Very true.
    That's my preference as well, although I don't have anything against EDA tools
    that merely reference library parts in their design files so long as there's a
    function to create a standalone library file that contains all the reference
    parts (PCAD did it this way).

  15. xray

    xray Guest

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