Keep a route's own vias apart while it is searched

Committed vias were checked for hole spacing, but a route's own vias are
not committed until it is done, so a route hopping layers (more of them
on 6 layers) could put two of its vias 0.41 mm apart, as th-eda's
6-layer flight controller showed. A via is now also checked against
layer changes earlier on its own route.

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/exact_router.py

@@ -215,7 +215,8 @@ def route_board_exact(
         # connections of one net that end on the same plane cell share its
         # via: write it once, and never on top of a via already on the board
         acc.vias.extend(
-            v for v in dict.fromkeys(vias) if v not in acc.vias and (net_no, v) not in fixed_vias
+            v for v in dict.fromkeys(vias)
+            if v not in acc.vias and not _on_fixed_via(net_no, v, fixed_vias, via_half)
         )
         for box, box_layers in boxes:
             oid = next(owner)
@@ -645,6 +646,15 @@ def _end_in_rule_area(tree, wires, half_width) -> bool:
     return False
 
 
+def _on_fixed_via(net_no, point, fixed_vias, via_half) -> bool:
+    """A routed via that reuses a via already on the board: the grid put it
+    on the fixed via's cell, a little off its centre, and it is not written."""
+    return any(
+        net == net_no and abs(loc.x - point.x) <= via_half and abs(loc.y - point.y) <= via_half
+        for net, loc in fixed_vias
+    )
+
+
 def _copper_boxes(wires, vias, half_width, via_layers, via_half=None):
     via_half = via_half or half_width
     boxes: list[tuple[IntBox, frozenset[int]]] = []

src/freeroute/route/grid_router.py

@@ -257,6 +257,7 @@ class GridRouter:
         # an own-net via at the very same cell, which it simply reuses.
         drill = via_drill if via_drill else 2 * self.via_half
         need = drill + max(hole_to_hole, 0)
+        self._via_drill, self._hole_gap, self._hole_need = drill, max(hole_to_hole, 0), need
         reach = math.ceil(need / self.step)
         self._hole_offsets = [
             (dx, dy)
@@ -265,7 +266,10 @@ class GridRouter:
             if (dx or dy) and math.hypot(dx, dy) * self.step < need
         ]
         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:
@@ -299,6 +303,24 @@ 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.
+        self._tht_holes: list[tuple[IntPoint, int]] = []
+        self._tht_block: set[Cell] = set()
+        for pin in board.get_pins():
+            if pin.shape is None or sum(1 for layer in pin.layers if layer in self.layers) < 2:
+                continue
+            box = pin.shape.bounding_box()
+            radius = min(box.ur.x - box.ll.x, box.ur.y - box.ll.y) // 2
+            reach = radius + self._via_drill // 2 + self._hole_gap
+            self._tht_holes.append((pin.location, reach))
+            ring = IntBox(pin.location.x, pin.location.y, pin.location.x, pin.location.y)
+            for cell in self._cells_in_box(ring, reach):
+                self._tht_block.add(cell)
 
     # --- grid helpers -------------------------------------------------------
 
@@ -516,6 +538,26 @@ class GridRouter:
                     return False
         return self._holes_clear(cell, net_no)
 
+    def _near_path_via(self, node: Node, cell: Cell, came_from: dict) -> bool:
+        """A layer change earlier on the route that reaches ``node`` sits
+        within hole spacing of ``cell`` (and is not the same through via).
+        Committed vias are checked elsewhere; a route's own are not yet
+        committed while it is searched. Looks back far enough to cover the
+        hole spacing twice over, not along the whole route."""
+        limit = 4 * (math.ceil(self._hole_need / self.step) + 1)
+        need = self._hole_need / self.step
+        steps = 0
+        while node in came_from and steps < limit:
+            prev = came_from[node]
+            changes_layer = prev[:2] == node[:2] and prev[2] != node[2]
+            if changes_layer and node[:2] != cell and (
+                math.hypot(node[0] - cell[0], node[1] - cell[1]) < need
+            ):
+                return True
+            node = prev
+            steps += 1
+        return False
+
     def _via_nets_at(self, cell: Cell) -> set[int]:
         nets = {net for net, n in self._via_nets.get(cell, {}).items() if n > 0}
         fixed = self._fixed_vias.get(cell)
@@ -524,7 +566,16 @@ class GridRouter:
         return nets
 
     def _holes_clear(self, cell: Cell, net_no: int) -> bool:
-        """No via centre within hole-to-hole reach, but an own-net one here."""
+        """No via centre within hole-to-hole reach, but an own-net one here,
+        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
@@ -633,6 +684,8 @@ class GridRouter:
                     pin = ends.get(node)
                     if ok and isinstance(pin, Pin) and self._walled(node):
                         ok = self._via_fits_at(pin.location, net_no)
+                if ok and self._near_path_via(source, cell, came_from):
+                    ok = False  # too close to a via earlier on this same route
                 if ok:
                     self._relax(source, target, g_via, goal_cell, g_score, came_from, open_heap)
                 continue
@@ -644,6 +697,8 @@ class GridRouter:
                     ok = via_ok.get(cell)
                     if ok is None:
                         ok = via_ok[cell] = self._via_placeable(cell, net_no, conns)
+                    if ok and self._near_path_via(current, cell, came_from):
+                        ok = False
                 else:
                     ok = True
                 if ok:
@@ -717,7 +772,23 @@ class GridRouter:
             ]
             copper += [(box, net) for net, _, box in self.board.get_fixed_copper()]
             self._static_copper = copper
-        return not any(net != net_no and box.overlaps(grown) for box, net in self._static_copper)
+        if any(net != net_no and box.overlaps(grown) for box, net in self._static_copper):
+            return False
+        return self._hole_clear_at(point)
+
+    def _hole_clear_at(self, point: IntPoint) -> bool:
+        """Hole spacing measured exactly from ``point`` to every via and
+        through-hole pad (a via moved into a pad is not on its cell's centre)."""
+        need = self._hole_need
+        if self._via_centres is None:  # rebuilt only after vias change
+            self._via_centres = [loc for _net, loc in self._fixed_via_points] + [
+                self._cell_center(c) for c, count in self._via_nets.items() if any(count.values())
+            ]
+        if any(math.hypot(c.x - point.x, c.y - point.y) < need for c in self._via_centres):
+            return False
+        return not any(
+            math.hypot(loc.x - point.x, loc.y - point.y) < reach for loc, reach in self._tht_holes
+        )
 
     def _stub_cells(self, pin_location: IntPoint, cell: Cell, half: int | None = None) -> list[Cell]:
         """Cells where another net's trace would come too close to the stub."""
@@ -993,6 +1064,8 @@ class GridRouter:
         for cell in conn.via_cells:
             count = self._via_nets.setdefault(cell, {})
             count[conn.net_no] = count.get(conn.net_no, 0) + 1
+        if conn.via_cells:
+            self._via_centres = None
         for cell, layer in conn.trace_cells:
             self._cell_owner[(*cell, layer)] = conn.index
         conn.half = half = self._conn_half(conn)
@@ -1071,6 +1144,8 @@ class GridRouter:
             count = self._via_nets.get(cell)
             if count and count.get(conn.net_no):
                 count[conn.net_no] -= 1
+        if conn.via_cells:
+            self._via_centres = None
         conn.via_cells = []
         conn.wires = []
         conn.vias = []

tests/route/test_fixed_wiring.py

@@ -91,3 +91,18 @@ def test_a_fanned_out_signal_is_routed_from_its_via():
     assert sig in exact.result.routed_net_numbers
     assert not exact.result.vias.get(sig), "the fan-out via is already there"
     assert {names[layer] for layer, _ in exact.result.wires[sig]} == {"B.Cu"}
+
+
+def test_the_session_never_repeats_copper_already_on_the_board():
+    # the JAR writes the DSN's wiring back into its session, and an applier
+    # then adds it a second time on top of itself; freeroute writes only
+    # what it routed
+    from freeroute.route.pipeline import build_exact_routing_result
+
+    fixed_vias = {(5000.0, -11500.0), (10000.0, -11500.0)}
+    fixed_paths = {(5000.0, -10000.0, 5000.0, -11500.0), (10000.0, -10000.0, 10000.0, -11500.0),
+                   (2000.0, -2000.0, 8000.0, -2000.0)}
+    result = build_exact_routing_result(parse_dsn(_FANOUT), resolution=2)
+    for net in result.nets:
+        assert not {(v.x, v.y) for v in net.vias} & fixed_vias
+        assert not {tuple(w.coords) for w in net.wires} & fixed_paths

tests/route/test_via_spacing.py

@@ -54,3 +54,83 @@ def test_connections_sharing_a_plane_via_write_it_once():
     vias = exact.result.vias[1]
     assert len(vias) < 8, "no via is shared, so this board no longer tests sharing"
     assert len(set(vias)) == len(vias), "a shared via written more than once"
+
+
+def _router(dsn_text, via_drill_um=300):
+    from freeroute.board import build_board
+    from freeroute.route.grid_router import GridRouter
+    from freeroute.route.pipeline import _rule_clearance_dsn, _rule_width_dsn
+
+    dsn = parse_dsn(dsn_text)
+    s = dsn.resolution.value
+    return GridRouter(
+        build_board(dsn), trace_width=round(_rule_width_dsn(dsn) * s),
+        clearance=round(_rule_clearance_dsn(dsn) * s), resolution=2, orthogonal=True,
+        via_drill=via_drill_um * s, hole_to_hole=250 * s,
+    ), s
+
+
+_THT = """(pcb tht (parser) (resolution um 10) (unit um)
+  (structure (layer F.Cu (type signal)) (layer B.Cu (type signal))
+    (boundary (path pcb 0  0 0  20000 0  20000 -20000  0 -20000  0 0))
+    (via "Via[0-1]_500:300_um") (rule (width 150) (clearance 150)))
+  (placement (component T (place J1 10000 -10000 front 0)))
+  (library (image T (pin tht 1 0 0))
+    (padstack tht (shape (circle F.Cu 1700)) (shape (circle B.Cu 1700)) (attach off))
+    (padstack "Via[0-1]_500:300_um" (shape (circle F.Cu 500)) (shape (circle B.Cu 500)) (attach off)))
+  (network (net SIG (pins J1-1))))"""
+
+
+def test_no_via_goes_near_a_through_hole_pads_hole_even_of_its_own_net():
+    router, s = _router(_THT)
+    pin = router._cell_of(router.board.get_pins()[0].location)
+    assert not router._holes_clear(pin, 1)  # own net, right on the pad
+    far = (pin[0] + 40, pin[1])
+    assert router._holes_clear(far, 1)
+
+
+def test_a_via_in_a_pad_keeps_hole_spacing_from_a_fixed_via():
+    from freeroute.geometry import IntPoint
+
+    text = _THT.replace("(network (net SIG (pins J1-1))))",
+                        "(network (net SIG (pins J1-1)))\n"
+                        "  (wiring (via \"Via[0-1]_500:300_um\"  3000 -3000 (net SIG) (type route))))")
+    router, s = _router(text)
+    assert not router._hole_clear_at(IntPoint(3400 * s, -3000 * s))  # 0.4 mm < 0.55 mm
+    assert router._hole_clear_at(IntPoint(3600 * s, -3000 * s))
+
+
+def test_hole_spacing_from_a_fixed_via_is_measured_from_where_it_really_is():
+    # a fixed via off the grid with its own 0.25 mm drill, and the router's
+    # via a smaller 0.2 mm one (the flight controller's case): a new via needs
+    # its centre 0.1 + 0.125 + 0.25 = 0.475 mm away, measured exactly, where
+    # one rule for all vias gave 0.2 + 0.25 = 0.45 from the cell centres
+    text = _THT.replace("(network (net SIG (pins J1-1))))",
+                        "(network (net SIG (pins J1-1)) (net GND))\n"
+                        "  (wiring (via \"Via[0-1]_500:250_um\"  3030 -3030 (net GND) (type route))))")
+    text = text.replace(
+        '(attach off)))\n  (network',
+        '(attach off))\n    (padstack "Via[0-1]_500:250_um" (shape (circle F.Cu 500)) '
+        '(shape (circle B.Cu 500)) (attach off)))\n  (network',
+    )
+    router, s = _router(text, via_drill_um=200)
+    via = next(v for v in router.board.get_items() if getattr(v, "drill", 0))
+    assert via.drill == 250 * s
+    loc = via.location
+    for cell in [(x, y) for x in range(router.cols) for y in range(router.rows)]:
+        c = router._cell_center(cell)
+        d = math.hypot(c.x - loc.x, c.y - loc.y)
+        if router.step * 1.5 < d < 470 * s:
+            assert not router._holes_clear(cell, 1), f"{d / s:.0f} um from the fixed via"
+        elif 560 * s < d < 700 * s and cell not in router._tht_block:
+            assert router._holes_clear(cell, 1)
+
+
+def test_a_route_keeps_its_own_vias_apart():
+    # a route that changed layer at (10, 10) may not change layer again one
+    # cell away; the same cell is the same through via, and far is fine
+    router, _s = _router(_THT)
+    came_from = {(10, 10, 1): (10, 10, 0), (11, 10, 1): (10, 10, 1), (12, 10, 1): (11, 10, 1)}
+    assert router._near_path_via((12, 10, 1), (11, 10), came_from)
+    assert not router._near_path_via((12, 10, 1), (10, 10), came_from)
+    assert not router._near_path_via((12, 10, 1), (40, 10), came_from)