From 9c82d285a3580ddd495eaa11e8dba87df5039577 Mon Sep 17 00:00:00 2001
From: Fredrik Thulin <fredrik@thulin.net>
Date: Mon, 25 Sep 2017 10:42:14 +0200
Subject: seems to work like this

---
 fix-layer-4.py | 111 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)
 create mode 100755 fix-layer-4.py

diff --git a/fix-layer-4.py b/fix-layer-4.py
new file mode 100755
index 0000000..59f7a1f
--- /dev/null
+++ b/fix-layer-4.py
@@ -0,0 +1,111 @@
+#!/usr/bin/python
+"""
+
+Layer 4 is a layer with large polygons (GND and Power). In Altium, this was made
+like an inverted layer with drawn lines separating polygons. Issues were with
+line thickness in Kicad, clearance parameters preventing copper to flow in between
+pins under the FPGA and the fact that KiCAD doesn't do inverted layers so the
+lines had to be removed and zone clearances adjusted to create the same result.
+
+Compare with
+
+  $ gerbv 'Cryptech Alpha-In4.Cu.gbr' CrypTech.GP3
+
+"""
+
+import sys
+import pcbnew
+
+
+def remove_tracks(board, layer):
+    """
+    The tracks on Layer four are actually where there *should not* be copper.
+    L4 is an inverted layer, but that information actually isn't in the files -
+    it is specified in an excel sheet sent to the PCB house.
+
+    By removing them and then setting some parameters carefully on the zones
+    on that layer, we get a close-to-perfect (but no longer inverted) result
+    in KiCAD.
+    """
+    for this in [x for x in board.GetTracks() if x.GetLayerName() == layer]:
+        print('Removing track {}'.format(this))
+        board.Delete(this)
+
+#def set_tracks_width(board, layer, width):
+#    for this in [x for x in board.GetTracks() if x.GetLayerName() == layer]:
+#        this.SetWidth(width)
+#
+#def move_tracks(board, from_layer, to_layer):
+#    for this in [x for x in board.GetTracks() if x.GetLayerName() == from_layer]:
+#        this.SetLayer(board.GetLayerID(to_layer))
+
+
+def layer_zone_fixes(board, layer):
+    for i in range(board.GetAreaCount()):
+        area = board.GetArea(i)
+        if area.GetLayerName() != layer:
+            continue
+        print('Area {} {}'.format(area, area.GetNetname()))
+        # This makes sharp edges matching Altium Designer
+        # 0.0255 is the minimum KiCad wants in order to allow changes to the zone inside KiCad
+        area.SetMinThickness(int(2 * 0.0255 * 1000000))
+        # 0.25 works better for the distance between zones in the bottom half of layer 4,
+        # but does not allow copper between the vias under the FPGA
+        #area.SetZoneClearance(int(0.25 * 1000000))
+        #
+        # Values below 0.15 or somewhere there does not seem to make a difference at all
+        area.SetZoneClearance(int(0.15 * 1000000))
+        if area.GetNetname() == 'GND':
+            area.SetPriority(50)
+            # 0.25 clearance on the 'background' GND zone keeps the distance to the island
+            # zones in the bottom half of layer 4, matching the clearance between the areas
+            # but creating a bit more clearance around vias in KiCAD plot than in Altium
+            area.SetZoneClearance(int(0.25 * 1000000))
+            area.SetThermalReliefCopperBridge(int(0.5 * 1000000))
+            #help(area)
+
+
+def hide_layers_except(board, layers):
+    """
+    As a convenience when working on getting a particular layer right, hide other layers.
+    """
+    lset = board.GetVisibleLayers()
+    print('Layer set: {} / {}'.format(lset, lset.FmtHex()))
+    #help(lset)
+    mask = 0
+    for x in lset.Seq():
+        name = board.GetLayerName(x)
+        print('  {} {}'.format(x, name))
+        if name in layers:
+            mask |= 1 << x
+    hexset = '{0:013x}'.format(mask)
+    visible_set = pcbnew.LSET()
+    visible_set.ParseHex(hexset, len(hexset))
+    board.SetVisibleLayers(visible_set)
+
+
+def main(in_fn='rev03-KiCad/convert.kicad_pcb', out_fn='rev03-KiCad/Cryptech Alpha.kicad_pcb'):
+    board = pcbnew.LoadBoard(in_fn)
+    pcbnew.SaveBoard(in_fn + '.before-fix-layer-4', board)
+
+    remove_tracks(board, 'In4.Cu')
+    #set_tracks_width(board, 'In4.Cu', int(0.15 * 1000000))
+    #move_tracks(board, 'In4.Cu', 'Eco2.User')
+    layer_zone_fixes(board, 'In4.Cu')
+
+    hide_layers_except(board, ['In4.Cu'])
+
+    # Only show Through Via while working on Layer 4
+    board.SetVisibleElements(0x7FFC0009)
+
+    pcbnew.SaveBoard(out_fn, board)
+    return True
+
+if __name__ == '__main__':
+    try:
+        res = main()
+        if res:
+            sys.exit(0)
+        sys.exit(1)
+    except KeyboardInterrupt:
+        pass
-- 
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