Custom footprints scripting using custom shape primitives

Layout Footprints
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I was wondering if there was a python script to make custom shapes in footprint using custom shape primitives.

To give some context, let’s say I would like to generate a pcb coil and generate a footprint with it. I generally use the bitmap to component and then manually edit the text file to move it to a different layer but this makes them invisible to the DRC and requires keep out zones or additional manual intervention.
The best of the bests would be to have a script converting a gerber or svg to custom shapes in footprint. This would make designing RF pcbs a fun job.
Writing the custom shape primitives by hand is a bit tedious.

When I saw the great plugin made by @maui I wondered if this was possible or already made.

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Yes: https://github.com/pointhi/kicad-footprint-generator

Extensively used for generating footprints for the official lib.

Note: this is a standalone library not intended to be used as a kicad internal script.

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If your design starts with i.e a dxf, you may also have a look at StepUp for (RF) footprint generation.
It is a manual process, but gives you a DRC safe footprint.

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@Rene_Poschl Thanks, that can be very useful for scripting.

@maui That’s exactly what I was searching for! Amazing! It is funny that I always use the KicadStepUp but I am still unaware of its full awesomeness…

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Do you have an example with a conversion of a logo to footprint’s copper zones?
For example when the svg is imported and results in BSplines (filled inside as if the sketch was padded in freecad)
I try to attach a freecad example logo.FCStd (7.2 KB)

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you need to convert the Sketch from Bspline to arcs and lines (because kicad doesn’t support bspline for Geometry pads), and then use it as a Pads_Poly pad (you can find an example in the StepUp FC Demo menu).
logo-fp.FCStd (43.1 KB)
fp-logo.kicad_mod (8.8 KB)

There is a specific button in StepUp to do it for you:

logo
logo832×1390 136 KB

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For logos you can also use https://github.com/badgeek/svg2shenzhen (you can use any vector format as input that is supported by inkscape and it exports your logo as a kicad footprint)

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That’s great! Thanks a lot

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Yes, I tried it before but it was not properly working into Inkscape and then I decided to do it using the bitmaptocomponent. I don’t know if it would be DRC compliant either.

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Unfortunately not … svg2shenzhen is not DRC complaint because it is using poly-lines and not primitive pads.
It is aimed to full artwork freedom.
StepUp is instead aimed to make footprint for pcb routing and will generate DRC complaint footprints.

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Last question: I tried to look into the demos but I was not able (probably my abilities as a truffle dog are not very good) to find a doc file that defined the keyword and their meaning and characteristics/requirements.
For example, F_Silks_0.16, Pads_Poly_Arc, Pads_Poly, …
Is there any such file?

Last last question: I see there is always a circle inside the Pads_Poly. Is that required?

Thanks again!

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Yes. It defines the anchor pad (requirement by the kicad file format)

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The only doc on creating footprint ATM is this file inside the demo Menu: Generating-a-KiCAD-footprint-and-Model-from-3D-Step-Data.pdf
This doc was added by an user and that was very welcomed…
…

Labels have some locked names to get parsed by the script…
The demo file complex-Polyline-footprint.FCStd is one of the most complex to be used as sample…
footprint-labels
F_Fab, FSilks, F_CrtYd have their size embedded in the label… i.e. F_Silks_0.16 means a F.SilkS draw with 0.16 mm in size.

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I see you pain, writing docs is always a big effort, sometimes even bigger than writing the tool itself. The only fun is to use LaTeX with tikz! :rofl:

Could you please point me to the part in the python code where those label are defined?
Their name is quite intuitive, but it might useful.

I am trying to substitute the copper areas of a quite complex logo with DRC compliant areas (unfortunately I cannot share it directly). The logo was made with the method I outlined before, changing the poly-lines to the desired layers.
My first idea was to import it using KSU and use it as a stencil to make the copper pads and then re-export it.
The first issue I encountered is that I cannot import poly-lines in freecad.
Therefore I decided to try to re make it from zero.
When I tried to make a shape with an empty area inside (like an O letter with some thickness), if I padded it using freecad, the solid is hollow, but if I export it as a single piece to a footprint, the hole inside was filled.
I saw the demo footprint-complex-arc-pads and also that the areas are split into three.

  • Is this required because hollow areas are not supported?
  • Is poly-lines footprint import not supported?

So I tried also a different method, but without KSU. I converted it as I was doing before with the poly lines, I added a pad into the copper poly-lines and in the right-click menu I found the option “Create pad from the selected shapes”. I was not expecting that, but it converted that shape to a proper pad!
This procedure is more of a workaround than solution, though, but it could also work with svg2shenzen I think.

Using KSU with freecad would still probably produce the best footprints, as it would use only the minimum number of required primitives.

Thanks again for your patience!

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inside the file ‘https://github.com/easyw/kicadStepUpMod/blob/master/kicadStepUptools.py’ search for:

def PushFootprint():

Why don’t you place a keepout area around your logo?

Which version of FreeCAD are you using… FreeCAD can import DXF and SVG containing poly-lines…
And StepUp can handle fp poly-lines import, but only if the poly-line will lead to a pad…

This is a requirement to create a kicad pad… only connected area can make a pad.

Anyway, for a logo design, definitely svg2shenzen is your best option. Still you will have to rework the footprint to get a DRC compliant fp.

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Can I place a keepout area directly inside the footprint? I will not be the only user of that footprint and I would like to avoid adding extra steps to place keep out areas on the pcb.

KSU is at commit c25f75b (Your branch is up-to-date with ‘origin/master’.).
Freecad is 0.18.3.
I see, it is not leading to a pad as it is a graphic for the silkscreen here and therefore not imported.

If I have a custom shape with a hole inside this should still be topologically connected. Let’s say you take the example before and close the two feet into one, creating a non-copper region inside a closed region. When converted to kicad_mod it will end in a footprint without the hole inside.
fp-Logo.kicad_mod (4.8 KB) logo-fp.fcstd (21.8 KB)
So, if I understand well this is not supported by kicad.

I struggled to get it working properly and I am in favour of the approach using a proper cad.
I am trying now using a complex logo to understand the limits of each approach, but the idea is to use it for complex coil shapes, antennas and meta-material RF elements.
Their shapes are sometimes quite exotic and they resemble more of a complex logo, but I can assure you there is a rationale behind their shapes and those might be scripted.
The final goal is to automatically create footprints for automatic inclusion in kicad, with full DRC support.

For example, as a test, I tried this (svg) shape:
customshapekicad
using svg2shenzen but I was not able to export it:
I am using Inkscape 0.92.4 (5da689c313, 2019-01-14) on Linux Kubuntu 19.10

Traceback (most recent call last):
  File "export.py", line 752, in <module>
    _main()
  File "export.py", line 748, in _main
    e.affect()
  File "/usr/share/inkscape/extensions/inkex.py", line 283, in affect
    self.effect()
  File "export.py", line 324, in effect
    self.processExportLayer()
  File "export.py", line 490, in processExportLayer
    with open(kicad_file, 'r') as f:
IOError: [Errno 2] No such file or directory: '/tmp/.svg2shenzhen-cache/customshapekicad.pretty/F.Cu_g824.kicad_mod'

I checked the folder and it is there, but the file is missing, but I suppose it should be created by the extension and not manually. I am not sure how to fix this error.

So then I tried the same shape again with the approach using freecad (custom.FCStd (9.3 KB) ) but the result is an oval without the inner hole, as discussed before.
Anyway, i tried again using the bitmap to component and I was able to make a single pad with a single primitive (custom_b2c.kicad_mod (9.9 KB) ), so it should be somewhat possible to have custom pads with custom shaped holes inside.
How would you convert this latest one using KSU? Should I always split it into two shapes and then combine them into two primitives for the same custom pad?

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I manged to get svg2shenzen to work. The executable in ~/.config/inkscape/extensions/svg2shenzhen/bitmap2component_linux64 needs to be executable.
chmod +x ~/.config/inkscape/extensions/svg2shenzhen/bitmap2component_linux64

Just for reference, this is done using svg2shenzen and converted into a pad using the method described before inside the kicad footprint editor customshapekicad.kicad_mod (8.8 KB)

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I’m glad you find your way… luckily kicad offers a human readable text for its formats, so many tools are implementing different and user oriented solutions.

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