How to modify an existing symbol

[rgmcleod52]

I’m a fairly new KiCad user. I’m using KiCad 7. I’ve done a couple of schematics for small projects.

What I’m trying to do is put a symbol for an Arduino Micro board in my schematic. I found an Arduino specific library on GitHub that included the Micro. I included it in my libraries for the schematic. When I inserted the symbol for this device into my schematic, I could see that the pin numbers were the same as the pin names. I really wanted the pin numbers to be numbers since the some of the pins have multiple functions and it’s easier to deal with that way.

So I opened the symbol editor and changed the pin numbers accordingly and saved it. All good. Or so I thought. I then made connections to this device on the schematic.

After saving the schematic, I went to create a PCB. When I went into the PCB Editor and Updated the PCB from the Schematic I got a bunch of warnings and errors.

The group of warnings were “Warning: No net found for symbol A1 pin 3V3” for example. I got one of these messages for each of the 34 pins on the device. The “3V3” was the name originally shown on the symbol as the description for pin 19 when I originally inserted it into the schematic.

The group of Errors were along these lines - “Error A1 pad 19 not found in PCM_arduino-library:Arduino_Micro_Socket”. Again, I got similar message for each of the 34 pins on the Arduino Micro. This one - pin 19 - is the one referenced above as the “3V3” pin.

How can I make changes to a symbol from a library such as this and have it reflect when I use the symbol and import it into a PCB design?

Rick

[ML9104]

Sounds like you forgot to tell the schematic that you changed the part in your library.
In the schematic, right-click on the symbol and select properties. Choose “Update symbol from library”.
Running an ERC is always a good idea and would have told you about issues.

[paulvdh]

@rgmcleod52

I found an Arduino specific library on GitHub that included the Micro.

There was no need to go to github. There is a template for the arduino micro built right into KiCad. You can access it via: Project Manager / File / New Project from Template

I am not sure what this means:

@rgmcleod52

I could see that the pin numbers were the same as the pin names.

@rgmcleod52

So I opened the symbol editor and changed the pin numbers accordingly and saved it.

Pin “numbers” in KiCad are 4 character strings that can use numbers and letters. BGA’s for example use the “chessboard” type of pin “numbering”. But the important thing here is that the pin numbers are used to map the pins in the schematic symbol to the pads on the footprint. A pin in the schematic maps to a pad on the footprint with the same name. If you change (only) the pin number in the schematic, you break this connection. If you want to change the pin numbers on the schematic, you have to change them in the footprint too. It may be easier to only change the pin name. You can change the pin name without any further complication.