Can't create NC symbol without footprint

[jonrbloom]

I'm trying to create an NC symbol so that I can tag arbitrary component pins as NC

Nothing I do allows me to bring the symbol into the schematic because there is no footprint. But if I include an empty footprint, then the board design includes these as blank footprints.

I read on the Eagle Forums that you can add an _EXTERNAL_ attribute to the device but this doesn't work either.

I even tried duplicating one of the 'frame' components and replacing the symbol but this also was rejected due to the missing footprint.

What is the correct method for creating schematic only symbols?

Why is everything in Fusion 360 Electronics so much harder than other packages!

[jesper8W75R]

@jonrbloom 
I don't quite understand what you are doing.
Why don't you just have the NC pins as part of the original device?

Anyway...
You need to have a device/component to pull in a symbol.
But you definitely do not need it to have a footprint.
I just tried.  It's very simple and straightforward.

1. Make new device.
2. Make a symbol

3. Add symbol to device
4. Save library.

5. Update design from library in your Schematic view.

Now you can add that component to a schematic, no problem.

[jonrbloom]

Thanks for the reply

"Why don't you just have the NC pins as part of the original device?"

Because then i must make a new device for each design if the NC's are not the same.

I am creating a device. But unless i also add a footprint I cant add it to the schematic. Fusion throws up an error that I can't add it because there is no footprint.

I read in another post that creating a symbol for an NC was a recommended approach to silence the DRC but there were no details given.

I will create a screencast this evening to demonstrate the error.

[jonrbloom]

Ok, so I had another play today.

If I create the symbol with no pins, then it does allow me to add it to my schematic.

However this doesn't achieve the goals of the NC because the DRC continues to report unconnected pins, even with the symbol attached (which is reasonable since there is no actual connection).

If I instead insert a pin into the symbol to act as the connection point, then Fusion refuses to let me add the device to the schematic because there is no footprint. And if I do create a footprint it cannot be blank because Fusion will then not let me associate it with the device, presumably because there are no pads!

The post <HERE> mentions that creating such a symbol is a recommended way but there is no description given on exactly how to define this.

[jesper8W75R · Accepted solution]

Okay, I see. 
I wasn't aware you were trying to silence the DRC.

Normally, that should not be a problem, as the only pins that the DRC will complain about are unconnected INPUT pins. (well and perhaps some PWR pins to odd supplies).
And, if a pin on a device are defined as IN, then it SHOULD be connected to something and you wouldn't need a NC symbol.

If I ever have a situation with the DRC, I shut it up by accepting the error.

For complex boards, this may be 100+ "errors" that come up. That's nothing to worry about.

I read Jorge's suggestion, but I think he perhaps haven't tried.
As you say, you cannot add it without a footprint, and you cannot have a footprint without a pad/hole (which you obviously doesn't want in this case).
Again, Fusion is playing the police, with no clue, and with you having NO chance to override its erroneous warning.

[jonrbloom]

@jesper8W75R - Thank you for jumping in to help.

You are right, my first post was not very clear. My head was a bit muddled after bashing around trying so many different experiments. I concentrated on the inability to add the symbol and forgot to mention the DRC part.

It was helpful to have your feedback that adding a symbol without a footprint is possible, since it forced me to go back and start from scratch and form a clear picture of which combinations are accepted and which are not.

It is a bit clunky, but I am content to use a combination of a symbol (with no pin or footprint) to annotate the schematic with an X, and a manual Accept of each of the DRC errors.