Reuse of schematic

Hi. This is my first post and Kicad is all a bit big and scary.

I have a design that was created for me (so I own the intellectual copyright) but the was a mistake in it and the designer has disappeared. So, I want to make a change to the existing schematic and the change the layout of the board. Before making the change, though, I wanted to have a go at creating my own layout with the existing schematic.

When I go in to the layout screen, I get the original layout and there are no issues. However, if I delete the layout and try to add the netlist, I get lots of “cannot add new symbol due to missing footprint” errors. I can’t see where I am going wrong and I couldn’t find any existing posts that cover this, so I hope you are able to help.

Thanks

I hereby certify that I am not simply asking someone else to design a footprint for me.

This is an auto-generated message that is in place on the “footprints” section of the KiCad.info forum. If I remove it and ask for a footprint to be designed anyway, I understand that I will be subject to forum members telling me to go design my own footprint or referring me to a 3rd party footprint site.

Since you are trying to reuse a schematic and do a layout, I suggest that you learn KiCAD from scratch…

Once you learnt how to use it, you will find out that you can export symbols from the schematic, and footprints from the layout and build those libraries which you can use in your re-used schematic and newly created layout.

Anyway, to extract footprints, you can use this option from the file menu in pcbnew:

image

Once you have done that, you need to re-assign missing footprints in the schematic editor and then generate the netlist…

Updating footprints is optional for existing PCB’s., and if you can not update them, (same as fetch brand new ones from the libraries), then there is something wrong with the library setup.

Also:

Working with a netlist in a separate file has been deprecated for 3 years or so now. Use: Eeschema / Tools / Update PCB from Schematic [F8] instead.

Overall I agree with elekgeek. Put in some time to learn KiCad.

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By deleting the layout you mean deleting everything in the PCBNew layout area and then importing your netlist? (I’m not going to get into the merits of changing workflow from importing netlist and updating directly from schematic, I don’t believe this is the issue.) If so, I think what might be happening is you don’t have the footprint libraries that your ghosted designer used. When applying the netlist from the schematic (either from a netlist file or directly by updating from schematic) PCBNew tries to fetch the assigned footprint (assigned in the schematic as a link to a footprint within a library) for components that aren’t already in the layout. Since by deleting all the footprints before loading the netlist you are forcing PCBNew to reload all the footprints from the libraries.

What might be better in your case is to delete everything except the footprints (and maybe the board outline). You don’t say what version of KiCad you are using, so I’ll assume the latest stable (v5.1.9). When you select objects (really useful for area selecting), you can right-click to get the contextual menu. In this menu there should be a Select item that will give a sub-menu. Within that sub-menu is an option to change the object-type filtering for that one selection. This should give you this dialog:
2021-04-12 12_05_39-Filter selection
Unselect footprints and board outline layer (if you don’t plan on redrawing it), click the OK button, and then press the delete key. This should preserve your footprints (and board outline if unselected) allowing you to import the net from the schematic. If all you are doing is relaying out the existing board first, you may not need to reimport the netlist because deleting items this way won’t delete any of the nets.

Hi,

thanks for all the suggestions. I have started learning it better and I’m starting to see a bit of light. I will have a go at the things you have said and get back to you, should i run into more problems.

Thanks!