Best way to show terminations on a schematic?

Hello, all,

I’m designing a circuit using a microprocessor board, an ATMega2560. I am not actively using all the pins, but I’m going to construct the PCB so that all unused pins terminate in a 5-hole strip of holes on 0.1 inch centers, like a perfboard. I’d like to show this on the schematic. I’m aware that schematics should only contain information of relavance to the electrical properties of the circuit, and that this leans more towards the physical, mechanical aspects of the PCB. Yet, in KiCAD, we have ‘Mounting Holes,’ which lean in this direction, too.

What’s the best (most industry standard) way of doing this? Here’s an example of my circuit, and the custom symbol and footprint I designed for it:
Screenshot from 2024-03-16 08-31-48



Thanks for any advice or guidance.


Halfway through reading your post I thought that I would probably design a custom schematic symbol for it myself, and then I read you already did exactly that :slight_smile:

I also sort of like your schematic symbol It’s compact and descriptive of it’s function, but for someone who is unfamiliar with it it probably looks “weird” the first time they see it, but that’s ok. When seeing something weird, a smart person spends a bit of time to investigate. Some kind of note on the schematic of what these symbols mean will help in this regard. I assume you have also hidden the RefDes of these symbols. (or your screenshot is not complete? ) When the RefDes is shown with a J, it will be clear quickly that this is some kind of connector.

On a side note, 5 holes is also a bit much. Breadboards have groups of 5 holes, but one is already used by the IC, and of the others, rarely more then 2 are used. Overall, I would rather have a grid of unassigned pads to make it easier to make (small) modifications later.

This could be an opportunity to use the array tool :grinning: :grinning: :grinning:

And it is goodnight from me.

@paulvdh, thanks, as always, for your quick and meaningful responses. You must live on this forum. I really value your thoughts and advice.

Yes, I made invisible the RefDes, to de-clutter the drawing. Your idea of showing a note of explanation is a very good one; I’ll implement that.

I choose 5 hole, because the Arduino AT Mega2560 clone that I’m using has 11 holes on a standard 0.1 inch pitch perfboard between the pin headers I soldered to the board. 5 holes gives the maximum connection points underneath the board for experimenters. The circuit I’m working from (one I’m copying from an existing project) mainly uses the outer connectors from the 2x pin headers on the Mega board. But you’re right, I’ll probably cut this down to 2 or 3 holes if they’re not underneath the microprocessor board.

Thanks, again, so much for your help and advice. Stay well.


Instead of making a custom symbol, when I want to do something like that, I just use the Conn_01x?? symbol and then the Connector_PinHeader_2.54mm:PinHeader_1x05_P2.54mm_Vertical footprint.

You’ll still have to connect the pads via a trace over in PCB, but that takes very little time.

Your approach is a bit cleaner. But, then you’ll probably need some text to explain what that strange symbol is. And you’ll have to create new ones any time you want to change the number.

Edit: I should have deleted the No Connect on GPIO13.