On 11/22/2011 02:44 PM, Brian F. G. Bidulock wrote: > Dick, > >> Then why are you here? What is your point? Make the patch contribution, >> all fields if >> you want, and I will personally give it extra consideration. >> >> If you are here to only create mischief and take shots, we can do without >> that. >> >> Contribute, do it like a team player, or go away please. >> >> This is your best chance, right here, right now, to be taken into this team >> or be shut out. >> > The changes are on my kicad-brian branch on launchpad > from a year ago. Pull away. > > > I'll also take this opportunity to explain to you why the > internal unit is a bug and increasing it is a bug fix and > not a feature: > > When I was laying out CBGA fields with metric spacing in > kicad, kicad moved every pad and via over to the next > decimil grid position. This causes several errors: > > 1. No pad is in it true position on a metric grid and is > no even in the correct position to a diagonal. > > 2. When placing vias between pads, each via was also off > the metric grid, sometimes adding in error to the pad > placement. > > 3. 45-degree dogbones between pads an vias could not make > a 45-degree angle (because pads and vias are not on the > diagonal, making a long dogbone and a little 1 mil jog > segment between the one end of the dogbone and the via > or pad. Unlocking the 45-degree track does not solve > the problem because the round-off jogs the endpoint of > the track and the 1 mil fragment reappears. > > 4. Pads are misplaced with respect to their drill holes. > > 5. Pads and vias must be dropped from 12 mil to 11.8 mil to > avoid DRC errors. Tracks must be dropped from 5 mil to > 4.8 mil to avoid DRC errors. (The DRC using integer math > rounds the other way from the grid error at points.) > > 6. Fabricator says we do 5 and 5 and to meet annular ring > requirements pads must be increased to 12 mil and tracks > increased to 5 mil; however, when that is done, they all > fail DRC on the fabricator's CAM tool. > > 7. The 5000 copper features on the board increase to about > 7000 due to the little 1 mil segments that cannot be > gotten rid of. Fabricator charges by number of copper > features (because the number increases the run time and > memory requirements of the CAM tool). So I have 2000 > features too many and have to pay for 4 and 4 instead > of 5 and 5. > > Please understand that the Gerbers given to a manufacturer > represents design data and has nothing to do with > fabrication limits. Round-off errors in the design data > simply add to the manufacturing tolerances making everthing > worse. CAM systems are quite accurate in their calculations > of DRC on design data. 3.5 metric Gerber data (3.6 is > better) is required to place everything in its true position > on both an imperial and metric grid. PCBNEW internal unit > must be a nanometer so that vias in a metric BGA pad field > are placed in their true design position. > > BTW, the 0.1-degree angle doesn't cut it either. > > This is why when I see someone take it upon themselves to > change the internal value to nanometers and get jumped on > for how the went about it rather disconcerting as a user. > Because, from a user perspective, I don't care whether int > was overloaded or macros are strewn everywhere: without a > precise internal unit, kicad is useful only for laying out > dimmer switches. > > Make the unit a nanometer, or better. Make the angle > 1/1000th of a degree, or better. Otherwise these same > problems will result on some board. > > --brian
Thanks Brian. That was helpful. Keep the faith. The internal units will get dealt with. There will be some discussion, with the goal of reaching a consensus on strategy, and then the changes will be made. This has always been the plan. What's different now is that man-hours are being committed to it, from a resource allocation standpoint, and the concerned parties have agreed to talk about it. Jean-Pierre has asked me to work with Vladimir to get it done. I had previously agreed to volunteer this time, and working with Vladimir was one of the discussed options. I will make a note to deal with the angle issue too, per your suggestion. Unfortunately I don't think pulling from your tree is going to be practical however, and this has to do with age and divergence. For now, I will begin to look over the internal units issues and then compare ideas with Vladimir when he is available again. Dick _______________________________________________ Mailing list: https://launchpad.net/~kicad-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp
