On Tue, Feb 07, 2017 at 01:57:53PM -0500, Wayne Stambaugh wrote: > On 2/7/2017 1:15 PM, Andy Peters wrote: > > > >> On Feb 7, 2017, at 8:16 AM, Nox <[email protected]> wrote: > >> > >> From a user point of perspective I would claim that the issue only raises > >> because there is the possibility to make pins invisible. Maybe someone can > >> explain to me the semantically need of invisible pins in general (beside > >> the fact that kicad needs it to solve n pads: 1 pin and global label > >> issues)? Would be changing the "invisible" flag to a "hide-if-stacked" > >> flag feasable? > > > > Professional electronics engineers and experienced layout people agree: > > invisible pins are a stupid idea and they should be banished. If you > > haven’t been screwed by invisible pins on a schematic, it’s only a matter > > of time. > > Maybe the reason I've never been bit by this in 30+ years is that I'm > not a professional. I've never found it particularly dangerous except > for new users who don't understand that electronics require power to > operate. Once you get over that hurdle, it's pretty obvious when your > footprint power pins aren't connected. That being said *always* check > you symbols and footprints. I don't care how much you paid from them or > from what vendor you got them from, there is always a chance that they > are incorrect. If they are incorrect and you did not check them, that > is *your* fault. That is something I learned my first year out of > college. AFAIK, it still applies.
And yet, mistakes still do happen, no matter how much checking is done. Software that is intelligently designed in a way that reduces the chance of mistakes is a very good thing, particularly when a lot of money is on the line. > > > > > I suppose that the original idea for invisible pins began back in the days > > of SSI and MSI logic, where everything had one power rail called VCC and > > also a ground rail, and to avoid cluttering up the schematic, it was > > convenient to make the power pins on each part hidden and give them > > appropriate net names. > > It was done so you didn't need to wire a whole bunch of pins in you > schematic that you knew needed to be connected to power. For us old > timers, this was obvious. Maybe they don't teach that in engineering > school any more. It also required less screen real estate. There were > no 28" high resolution monitors way back when. > > Almost every board I've ever designed has multiple supply rails because > I've mostly worked with analog I/O so the multiple supply argument is weak. > > > > > Of course, that’s an immediate fail, as TTL has a +5V rail, and 4000-series > > CMOS parts could have whatever rail (within reason) the designer deemed > > appropriate. > > > > Nowadays, with multiple rails on even simple designs, simply calling a > > power pin VCC and giving it the netname VCC and hiding it doesn’t work. > > > > And I see in this thread that there’s a use case — stacking power pins and > > hiding all but one, so when a wire is added to that one visible power pin > > it is added to all of them. That one can make a connection to an invisible > > pin baffles me. > > Both of these things baffle me. Stacking pins (visible or not) is much > scarier than invisible power pins. Connecting a wire to an invisible > pin just seems confusing to me. I'm guessing this is something that > just got overlooked but fixing it could be tricky. > > > > > Also, consider the technician who is bringing up a new board, or is trying > > to repair something. S/he wants to see power pins on the schematic, > > otherwise how can anyone begin to start debugging? > > > > I understand the desire to avoid cluttering up a schematic by hiding pins. > > I mean, we deal with monster FPGAs and CPUs here, and generally there’s a > > page on the schematic just for FPGA power connections (and the decoupling > > caps and all that). But hiding those pins has zero benefit and increases > > the chances of an expensive screwup. > > > > By all means, leave the capability for invisible pins in Kicad. But the > > standard libraries should never use them (for reasons Chris has mentioned) > > and their general use should be discouraged. > > Invisible pin support has to be maintained. I'm guessing some users > still prefer it and there are legacy designs which cannot be broken. As > for our standard libraries, we would have to get the buy in of our > library developers. I'm not sure how receptive they would be to the idea. > > > > > -a > > _______________________________________________ > > Mailing list: https://launchpad.net/~kicad-developers > > Post to : [email protected] > > Unsubscribe : https://launchpad.net/~kicad-developers > > More help : https://help.launchpad.net/ListHelp > > > > _______________________________________________ > Mailing list: https://launchpad.net/~kicad-developers > Post to : [email protected] > Unsubscribe : https://launchpad.net/~kicad-developers > More help : https://help.launchpad.net/ListHelp _______________________________________________ Mailing list: https://launchpad.net/~kicad-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp
