-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 10/12/2010 03:07 PM, Dick Hollenbeck wrote: > > Alex, I said nothing about metric. > > PCBNEW > ------ > > I'd like to see support for both metric and imperial (which we mostly > have), along with the 3rd notion of integer based internal units. The > problem we have now is that the granularity of the internal unit is not > fine enough to avoid round trip conversion errors. The finer we go, the > more memory the internal "cell" based autorouter (in PCBNEW) needs, and > the longer it will take. The change in memory and speed will likely be > related to the square in the granularity change. So if you increase the > granularity by 100, then you'll need 10,000 times as much memory and > time to run it. > Last time I checked, the autorouter took more resources and time to tackle a job if the grid in PCBNEW was reduced in size. It may be just my impression, but if you don't select a nanometer-grid, the autorouter won't use one. I last used the autorouter two months ago, so things might have changed.
> (So maybe you decide at that point to simply toss it out and use > freerouter.) > > If you take the autorouter off the table, then the question becomes, "is > there a downside to having granularity that is finer than you need?" > This is a question, not a suggestion. > The only downside that I see is the limitation in board size. Of course, with a 64-bit represantation you can use femto-scale units (smaller than an electron) and still have an 18km board. I don't see a downside. > Here is a posting which claims to have found the greatest common > denominator, GCD, for a new internal unit: > > https://lists.launchpad.net/kicad-developers/msg03757.html > > Here is another opinion: > > https://lists.launchpad.net/kicad-developers/msg03729.html > > > Here is the root of the thread: > > https://lists.launchpad.net/kicad-developers/msg03720.html > Mathematically correct. 20nm minimum, and there's no reason to not go as safe as 1nm. I agree > Until we revise the file format for PCBNEW, along with a comprehensive > migration plan, including a *.brd board converter, the best we can do is > plan and summarize, and schedule for later completion. Why not have a flag that specifies the unit used in the file? When the footprint is loaded, it's automatically converted to the proper internal unit. > A summarizing > paragraph could be formulated on this mailing list and then copied to a > blueprint after it is agreed to by a majority, inclusive of someone > willing to do the work. > Draft: The internal unit system of kicad shall be implemented as 1nm (one nanometer). A nanometer-scale internal unit enables the _exact_ representation of metric units _and_ imperial down to 1/100 (one hundredth) mil. Preferrably, support for nanometer-scaling would be provided by conditional compilation. A flag would be added to CMakeLists.txt to enable conditional compilation for nanometer support. Once support reaches a stable and usable state, old code may be removed. Hope this sounds reasonable. Feel free to correct and complete Alex -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org/ iQIcBAEBAgAGBQJMtGQbAAoJEL0kPHNPXJJKGFkP/01lGWRNevnATOh8k4I+vgM+ iyyVS3f+UIZ+lOvBS5/n/UXbefbyCvA3pA3WhpzTBi5x2DZ7Lq6gwtzYGQHv/Q1W P/F1iUnUbhUUO4+UVsK/TI/BWovNoULXuB+7WRsCr0uePDbysy8ISdBNYdLbQVDf mcUSV7W6jmRmEXp3B8lqLabC7tCCIMJqRAA6nPYGOkPG4kn4ZOrpL/LNcUGP+tCd usXQoxVG49czlJh3ridtxDVpF1U/+15zOYxl8tHiEue8pq9QExE/r9DdWUyFlOYR fzKZjyAz7vtdZIudlgFyB5H3lsOZGIMFcWkSby1g8+8IyIpumSjKAxvoLqZCYB5B 44mtMtR7ao5RzbzO/LvRKF392ybk6UjwIMS1CGangQJsyL9BgcqKv9Efe1kGVCTd O7C1zfjo6hBEvXlSpTIWt2QENFt1tWGHDA4lDGyKNle25HkkGvW2BcQ1kPu9iqHd 6VnAvWzHiRH4k99kSRGH6zrMA2hrfPhEJbcBjhgn/cS5p2zpHx5DEwHYeYEXxoel e9sZYvga6xTrIqcU8MzhRGiIDqz/LWV59q1Yc4bNAITkzS+Kg9YxZNM8IAIqPqVW +lQp9rVRp6IzW5O2cBpHHr1y13swOFilYNZ03kmv+tzqVXiokIR32j5jTufS20Zy NQCTtjdKX97SesQ91irn =7scy -----END PGP SIGNATURE----- _______________________________________________ Mailing list: https://launchpad.net/~kicad-developers Post to : kicad-developers@lists.launchpad.net Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp
