>> Invisible pin support has to be maintained. I'm guessing some users
>> still prefer it and there are legacy designs which cannot be broken.
Couldn't invisible pins become visible? As a transition make them grey
or something?
Just changing how they are displayed would not break any designs. Not in
its current implementation. But some support for stacked pins would be
needed before that.
- Kristoffer
On 2017-02-07 20:15, Chris Pavlina wrote:
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
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