Custom grid scale does not allow to select custom grid, and problem with alignment

Issue #56 resolved
created an issue


I have the following problem. I generated the TQFP144 footprint for Xilinx CPLD. I want to route the pins, however...

I can't get the route right in the center of the pad, or the routes are not evenly placed (y axis which should be the same for both).

I thought I might need to change the grid size, because snapping to smaller grid would allow me to adjust routes properly, but when I enter custom grid 0.0125" instead of default 0.05" it jumps to 0.317mm. There is no way to set custom grid size.

Comments (8)

  1. Razen repo owner

    Hm, that's strange. The route tool should auto snap to the centre of a pad.

    I created a test tqfp144 package and routed pins correctly both with the default 0.05" grid and a custom 0.25mm grid (which puts a grid point in the middle of each pin).

    To set a custom grid size click the grid size number next to the layout/schematic button. Clicking the unit will just toggle between inches and mm.

  2. Mateusz reporter

    I start with default 0.05 in, than I click number and set it to 0.0125, but its switching to 0.317mm, when I click on mm to switch to in I get back my 0.05

    I can make a movie of it if you need...

  3. Razen repo owner

    Ahhh, ok. I see the issue. 0.0125" is 0.3175mm (317.5um) and the grid scale is currently stored as an integer in um, which is causing the rounding.

    So it looks like you can set an exact 0.0125" grid at the moment! Sorry, I'll fix that as soon as possible.

  4. Razen repo owner

    I'm going to have to change the base dimension representation from um to nm. In the current system (um) you can't exactly represent 0.0125" (317.5um) whereas you can in nm (317500nm).

    Initial implementation is v0.7.5 but the main work will be in the next release.

  5. Mateusz reporter

    What is wrong with floating point representation ? I think mm are standard unit. If you use nm thats 10000000 for 1cm. Isn't it better to stick with mm and use floating point numbers ? Anyway I doubt boards are made with precission of nm, but I am not an expert.

  6. Razen repo owner

    Unfortunately many of the core algorithms need exact precision to function correctly. Most CAD programs use integer positioning (but often have the user decide on the unit which is then stored in the project file). I know that KiCAD and GEDA use (integer) thousanths of an inch (mils) as the base unit.

  7. Razen repo owner

    Fixed in v0.7.6. Core unit is now 0.1um which provides accurate 0.001 inch representation. Re-save parts and projects to update to new units.

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