Add mutual capacitance button wizard

This adds a python script to build a mutual capacitance button per the
document from http://ww1.microchip.com/downloads/en/appnotes/doc10752.pdf

(cherry picked from commit 1ebf7d349b)

mutualcap_button_wizard.py

@@ -0,0 +1,122 @@
+#  Copyright 2019-2020 Julian Fellinger
+#
+#  This program is free software; you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation; either version 2 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software
+#  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+#  MA 02110-1301, USA.
+
+import FootprintWizardBase
+import pcbnew
+from pcbnew import *
+
+class MutualcapButtonWizard(FootprintWizardBase.FootprintWizard):
+
+    def GetName(self):
+        """
+        Return footprint name.
+        This is specific to each footprint class, you need to implement this
+        """
+        return "Mutualcap Touch Button"
+
+    def GetDescription(self):
+        """
+        Return footprint description.
+        This is specific to each footprint class, you need to implement this
+        """
+        return "Wizard for Mutual Capacitance Touch Buttons."
+
+    def GetValue(self):
+        return "TouchButton-{width:g}x{height:g}mm".format(
+            width = pcbnew.ToMM(self.pads["Width"]),
+            height= pcbnew.ToMM(self.pads["Height"])
+            )
+
+    def GenerateParameterList(self):
+        self.AddParam("Pads", "Width", self.uMM, 12)
+        self.AddParam("Pads", "Height", self.uMM, 12)
+        self.AddParam("Pads", "Outer electrode width", self.uMM, 1)
+        self.AddParam("Pads", "Inner electrode width", self.uMM, 0.1)
+        self.AddParam("Pads", "Draw line around button", self.uBool, True)
+
+    @property
+    def pads(self):
+        return self.parameters["Pads"]
+
+
+    # build a rectangular pad
+    def smdRectPad(self,module,size,pos,name):
+        pad = D_PAD(module)
+        pad.SetSize(size)
+        pad.SetShape(PAD_SHAPE_RECT)
+        pad.SetAttribute(PAD_ATTRIB_SMD)
+
+        layerset = pcbnew.LSET()
+        layerset.AddLayer(pcbnew.F_Cu)
+        pad.SetLayerSet(layerset)
+
+        pad.SetPos0(pos)
+        pad.SetPosition(pos)
+        pad.SetName(name)
+        return pad
+
+    # This method checks the parameters provided to wizard and set errors
+    def CheckParameters(self):
+        pass
+
+    def BuildThisFootprint(self):
+        # o refers to the outer (drive) electrode
+        # i refers to the inner (receive) electrode
+        w   = self.pads["Width"]
+        h   = self.pads["Height"]
+        oew = self.pads["Outer electrode width"]
+        iew = self.pads["Inner electrode width"]
+        drawBox = self.pads["Draw line around button"]
+
+        oFingerCount = int((w-3*oew-iew)/(1.5*oew+iew))
+        oBorderWidth = (w-oew-iew-oFingerCount*(1.5*oew+iew))/2
+        clearance    = oew/2
+
+        ###border h
+        self.module.SetLayer(F_Cu)
+        size_pad = pcbnew.wxSize( w, oew )
+        self.module.Add(self.smdRectPad(self.module,size_pad, pcbnew.wxPoint(0,(-h/2)+oew/2),str(1)))
+        self.module.Add(self.smdRectPad(self.module,size_pad, pcbnew.wxPoint(0,( h/2)-oew/2),str(1)))
+        ###border v
+        size_pad = pcbnew.wxSize(oBorderWidth, h-2*oew)
+        self.module.Add(self.smdRectPad(self.module,size_pad, pcbnew.wxPoint((-w/2)+oBorderWidth/2,0),str(1)))
+        self.module.Add(self.smdRectPad(self.module,size_pad, pcbnew.wxPoint(( w/2)-oBorderWidth/2,0),str(1)))
+
+        xPos = -w/2+oBorderWidth+clearance+iew
+        oFingerSize = pcbnew.wxSize(oew/2, h-oew-iew-2*clearance-oew)
+        iFingerSize = pcbnew.wxSize(iew,h-2*oew-2*clearance)
+        #horizontal inner electrode trace
+        self.module.Add(self.smdRectPad(self.module,pcbnew.wxSize(w-2*oBorderWidth-2*clearance,iew), pcbnew.wxPoint(0,h/2-oew-clearance-iew/2),str(2)))
+        for i in range(0,oFingerCount):
+            #inner electrode fingers
+            self.module.Add(self.smdRectPad(self.module,iFingerSize, pcbnew.wxPoint(xPos-iew/2 ,0),str(2)))
+            #outer electrode fingers
+            self.module.Add(self.smdRectPad(self.module,oFingerSize, pcbnew.wxPoint(xPos+oew*0.75,-w/h-oew-iew/2+oew/2),str(1)))
+            xPos += oew*1.5+iew
+
+        #rightmost inner electrode finger
+        self.module.Add(self.smdRectPad(self.module,iFingerSize, pcbnew.wxPoint(xPos-iew/2,0),str(2)))
+
+        textSize = self.GetTextSize()
+        self.draw.Value(0, h/2+textSize, textSize)
+        self.draw.Reference(0, -h/2-textSize, textSize)
+
+        #optionally draw silkscreen line around button
+        if(drawBox):
+            self.draw.Box(0,0,w,h)
+
+MutualcapButtonWizard().register()