Hole spacing to a fixed via measured from where it is, with its own drill

A fixed via sits anywhere, not on a cell centre, and may have a bigger
drill than the router's via; checking hole spacing between cell centres
with one drill let the flight controller's routed 0.2 mm via come 0.19
mm from a hand-placed 0.25 mm one. The board now carries each fixed
via's drill (from KiCad's padstack name), and cells are checked against
fixed vias exactly.

src/freeroute/board/build.py

@@ -23,6 +23,7 @@ the containment invariant, and pads are centre-symmetric in practice).
 from __future__ import annotations
 
 import math
+import re
 
 from freeroute.dsn.model import DsnBoard
 from freeroute.dsn.shapes import Circle, Path, Polygon, Rectangle, Shape
@@ -38,6 +39,9 @@ from .transform import CoordinateTransform
 
 __all__ = ["build_board"]
 
+# DSN units per micrometre, for drills KiCad gives in um in via padstack names
+_DSN_PER_UM = {"um": 1.0, "mm": 0.001, "mil": 1 / 25.4, "inch": 1 / 25400}
+
 
 def build_board(dsn: DsnBoard) -> BasicBoard:
     """Construct a :class:`BasicBoard` from a parsed :class:`DsnBoard`."""
@@ -503,10 +507,15 @@ def _insert_wiring(dsn: DsnBoard, board: BasicBoard, transform: CoordinateTransf
         location = transform.dsn_to_board_point(via.x, via.y)
         pad = _pad_tile(max(padstack.shapes, key=_shape_extent), transform)
         box = pad.bounding_box()
+        drill = re.search(r"_([\d.]+):([\d.]+)_um", via.padstack)
+        drill_board = (
+            round(transform.dsn_to_board(float(drill.group(2)) * _DSN_PER_UM.get(dsn.unit, 1.0)))
+            if drill else 0
+        )
         board.insert(
             Via(
                 net_nos=[numbers[via.net]], fixed=True, padstack_name=via.padstack,
-                location=location, layers=sorted(layers or signal_layers),
+                drill=drill_board, location=location, layers=sorted(layers or signal_layers),
                 shape=IntBox(box.ll.x + location.x, box.ll.y + location.y,
                              box.ur.x + location.x, box.ur.y + location.y),
             )

src/freeroute/board/items.py

@@ -117,6 +117,8 @@ class Via(Item):
     #: layer indices the via's pads occupy, and the largest pad as a box
     layers: list[int] = field(default_factory=list)
     shape: object = None
+    #: drill diameter in board units, when the padstack name gives it
+    drill: int = 0
 
 
 @dataclass

src/freeroute/route/grid_router.py

@@ -268,6 +268,8 @@ class GridRouter:
         self._via_nets: dict[Cell, dict[int, int]] = {}  # routed via centres
         self._via_centres: list[IntPoint] | None = None  # cache for _hole_clear_at
         self._fixed_vias: dict[Cell, int] = {}
+        # fixed vias sit anywhere, not on cell centres: exact hole checks
+        self._fixed_holes: list[tuple[IntPoint, int]] = []
         self._fixed_via_points: set[tuple[int, IntPoint]] = set()
 
         if layers is None:
@@ -301,6 +303,9 @@ class GridRouter:
             if isinstance(item, Via) and item.fixed and item.net_nos:
                 self._fixed_vias[self._cell_of(item.location)] = item.net_nos[0]
                 self._fixed_via_points.add((item.net_nos[0], item.location))
+                # its own drill, from KiCad's padstack name (Via[0-3]_500:250_um)
+                reach = self._via_drill // 2 + (item.drill or self._via_drill) // 2 + self._hole_gap
+                self._fixed_holes.append((item.location, reach))
         # Through-hole pads have holes too, and a route changes layer at one
         # for free, so no via (of any net) goes within hole spacing of one.
         # The DSN has no drill for a pad; its smaller half size stands in.
@@ -545,6 +550,12 @@ class GridRouter:
         and no through-hole pad's hole within reach at all."""
         if cell in self._tht_block:
             return False
+        if self._fixed_holes:
+            here = self._cell_center(cell)
+            for loc, reach in self._fixed_holes:
+                d = math.hypot(loc.x - here.x, loc.y - here.y)
+                if d < reach and d > self.step:  # beyond its own cell: too close
+                    return False
         if self._via_nets_at(cell) - {net_no}:
             return False
         cx, cy = cell