topic How to get unconnected pins to pass ERC in EAGLE Forum

How to get unconnected pins to pass ERC

karl — Tue, 08 May 2018 01:28:41 GMT

I'm using an OLD version of Eagle (4.16r2) about which I have several questions:

I have some parts in my schematic that have unconnected pins (e.g. unused GPIO pins on a microcontroller). How can I get ERC to stop throwing warnings/errors over these?
What's the difference between an ERC error and ERC warning?
When I connect a VCC pin on a part to a VCC symbol (imported from the supply library), ERC throws an error, regardless of whether the pin's direction is set to Supply or Power (though it's a different error depending on the direction). Same for GND. How can I avoid this?

Thanks for any help.

Re: How to get unconnected pins to pass ERC

karl — Tue, 08 May 2018 03:09:47 GMT

Well, I temporarily fixed the unconnected pins problem by redefining the part with the pin in question as NC, though I may not always want it that way. At least ERC doesn't throw the unconnected pin errors anymore. It would be better if I could do that within the schematic instead of the part.

Re: How to get unconnected pins to pass ERC

one-of-the-robs — Tue, 08 May 2018 08:32:35 GMT

ERC only produces the unconnected warning for some pin directions. As you've observed, NC is not one of them (obviously) but neither is I/O (or, at least, it's downgraded to warning not error, it's a while since I used V4 and it may have changed). An unconnected input pin is always an error - in real life as well as in ERC - but an unconnected output isn't necessarily.

I don't think Eagle makes a big distinction between errors and warnings but it's intended that the former need to be addressed while the latter may be intentional, just unexpected. Connecting a power pin called VCC to a supply net called +5V would be a warning, for example, as it may well be intentional.