I finally finished my first schematic and everything looked great. I went ahead to perform Electrical Rules Check.

There were many errors.

Most of them were:

Pin connected to other pins, but not driven by any pin.

Pin not connected (use a "No-connection" flag to suppress this error).

I used bi-directional pins exclusively.

Also note that I used the Arduino shield template. Maybe I had to declare all pins not used as NC?

If you want, I can upload the schematic file somewhere.

EDIT: Here is a picture of the schematic.

enter image description here

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    \$\begingroup\$ You can try this out yourself without asking here. Do it in a limited way on one chip then bingo; see what happens. Do the errors reduce in number? \$\endgroup\$
    – Andy aka
    Nov 15, 2020 at 13:10
  • \$\begingroup\$ @Andyaka try what exactly? I declare all pins i did not use as NC. The arduino pins are way to many. Do i have to declare all of them NC? Maybe if declaring them as NC will break something since it is a shield? In one video i saw, he didn't label the header pins as NC. \$\endgroup\$ Nov 15, 2020 at 13:12
  • \$\begingroup\$ with 533 reputation, you should be able to include images directly in your question – So, what I usually do is using "plot" to write the schematic to an SVG file, and then hosting that myself and just <img src="https://url.of.my.image/file.svg" alt="schematic image"> in the post, or I open the SVG in Inkscape and export as PNG, and upload it directly using the "upload image" button in the post editor here. \$\endgroup\$ Nov 15, 2020 at 13:12
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    \$\begingroup\$ @user1584421 you're missing Andy's point. While they certainly are many, it's easy to just compare the results of two DRC runs ofter just changing one thing. (if in doubt, the difftool is very mighty). \$\endgroup\$ Nov 15, 2020 at 13:13
  • \$\begingroup\$ @MarcusMüller Thanks. I exported to svg but the image is weird. Like a checkerboard. Should i upload this photo? \$\endgroup\$ Nov 15, 2020 at 13:16

1 Answer 1


Looking at the circuit and where the ECR arrows are pointing I can see two type of violations

  1. undriven net
  2. Power flag

P1, P3, P4, P5, P6, P7 have pins that do not connect to anything. You are obviously labeling them to align to the Mega but from the perspective of this circuit they are unconnected. The intent of this ECR is to ensure you don't leave unconnected nets ... unconnected. If you intend to leave it unconnected us the "no connect" flag at the end of the net (the blue cross)

You have a couple of global powerflags (3v3, 5v, GND) but KiCAD does not know these are power, use the power_flag to inform kicad this is a powernet

Dangling nets:

if you are 100% sure a net is to be unconnected, add the NC to each one

enter image description here


if you are using power symbols that do connect to a pin that expects POWER-IN, inform Kicad that this is a power source

enter image description here

  • \$\begingroup\$ Thank you! I am new to KiCAD, and i am trying to understand what you just said. I do not exactly understand which {P1, P3, P4, P5, P6, P7} you are refering to. This is the arduino MEGA template, i just connected some pins that connect to my circuit. The green arrows are too many, should i label every pin where is a green arrow as NC? Then about the powerflags. There are two power signals in my circuit. Both coming from the coaxial connector (+arduino GND, but it also connects to the coaxial connector, so i said two). Should i just label the two lines that touch the connector? Is this enough? \$\endgroup\$ Nov 15, 2020 at 16:23
  • \$\begingroup\$ @user1584421 thats not too many ;) I had over 300 when I was dealing with an FPGA recently. To permit the ECR to complete a net must connect to two nodes. Dangling nets could indicate an incomplete circuit or an intentional no-connect. add a NC to each one to inform the checker of your intentions. The POWER-NODE. I am speculating here as you have not provided the infomation \$\endgroup\$
    – user16222
    Nov 15, 2020 at 17:47
  • \$\begingroup\$ my objection is not the work to do. I just ask, should i mark all the arduino pins that are not connected as NC? And about the labels.. Marking the signals that connect to the two poles of the power jack will be enough? Thanks again! \$\endgroup\$ Nov 15, 2020 at 17:51

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