Most people go through this process at first, but you seem to have got
hold of the basics pretty quick.

The purpose of power flags is to tell the ERC checking system that there
is actually power being provided.

Consider if your battery was a separate box and you connected it with
flying leads to a connector.

You would need to put a power flag on the ground and +volts pins to keep
ERC happy.

The gotcha that sometimes catches people out (but not you) is that a
regulator is often defined with it's output pin as a power out, in that
case you do not need a power flag on the regulator output.

If you have invisible pins set to invisible, then yes again you are
correct, these pins are automatically connected for you. This makes the
cct MUCH neater when you have a lot of devices. With only one or two
devices it does not make much difference. However if you make the
invisible pins visible you then HAVE to connect them manually.

With a uP such as the mega setting the pins to tri state is not really the
correct way to go but it is a good starting point. Really you should set
the pins to match whatever mode you are programming them to be. There is
NOT a one size fits all setting for them. (I'll bet that a lot of users
set the pins to passive and don't bother to change them for each design.
That will work, but you can lose a lot of the ERC checking) 

With the HC595, I assume that you copied the same device twice. If so
that should be OK. If this was an invisible pin then it should be
automatically connected unless you changed the name for some reason. If
you are manually connecting the power lines, then watch out for junctions.
A junction is NOT automatically created when two lines join, you need to
place a junction marker. 
With the reset pin issue, yes the warning is correct. You have to change
the pin type to passive or similar I think setting it to type input
will cure the problem as well, or another method is to pull up the pin
via a resistor then the error will go away. 

Power in pins should only connect to power out pins directly according to
the ERC rules. So when you try connecting a power out to something else
then you get this error. It's down to the uP being rather more clever
than the ERC system, so you have to make some allowances, you soon get
used to it :-)


On Sun, 22 Aug 2010 14:26:27 -0400
Robert Bieber <> wrote:

> Sorry if these are horrifically stupid questions, I'm just getting 
> started out trying to use Kicad.  My first project is putting together a 
> simple timer, and I'm running into a little trouble in EEschema dealing 
> with pin types and the VCC/GND power ports.
> First I had to build a new part for the Atmega328p I'm using, since 
> there wasn't one in the library.  I set all the I/O pins to 3 state and 
> the VCC/GND pins to power in, which as far as I'm aware is the right way 
> to do it...I hope I'm correct there.
> Now in my schematic, I've got a battery connected to a power regulator 
> with some filtering caps and such, and the ground of all that is 
> connected to the GND power port and the 5v output connected to the VCC 
> power port, and that seems to working correctly for the most part, as 
> I've connected VCC and GND on the 328 to those ports and they're not 
> complaining.  There are still a couple of issues, though:
> - I have two 74HC595 shift registers in the schematic, the VCC and GND 
> pins of which are invisible, but seem to be automatically connected to 
> the appropriate power ports.  However, one of them (but not the other) 
> is giving me the warning "Pin power_in not driven" on its GND pin, even 
> though I know that the GND port is properly connected to the power 
> regulator, and all the other GND connections on the schematic work 
> fine.  What could be causing this?
> - When I connect the RESET pin on the 328 to VCC, it gives me the 
> warning "Pin 3state connected to pin power_in".  The warning also 
> appears on the VCC pin of one of the shift registers (the same one that 
> gives the warning about the undriven GND pin).  Is there anything in 
> particular I need to do about this?  I did connect a 3state pin to a 
> power in pin, but why is that considered warning-worthy?
> Sorry if I'm missing something obvious, and if anyone has a better 
> source of documentation than the FAQ on the Kicad site, feel free to 
> direct me to it.
> -Robert Bieber
> ------------------------------------
> Please read the Kicad FAQ in the group files section before posting your 
> question.
> Please post your bug reports here. They will be picked up by the creator of 
> Kicad.
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