Initial Ti375 GNSS IMU board design and documentation

scripts/prepare_freerouting_dsn.py

@@ -0,0 +1,52 @@
+#!/usr/bin/env python3
+"""Compensate Freerouting 2.3.0's KiCad-10 DSN clearance scale mismatch.
+
+KiCad exports widths and clearances in micrometres.  Freerouting 2.3.0 keeps
+the widths but internally imports DSN clearance values at one quarter of the
+intended physical value.  Scaling only ``(clearance N)`` entries by four makes
+the router's physical rules match the source KiCad board.  Coordinates, track
+widths, vias, drills, padstacks, and keepouts are deliberately untouched.
+"""
+
+from __future__ import annotations
+
+import argparse
+import re
+from pathlib import Path
+
+
+CLEARANCE = re.compile(r"(\(clearance\s+)(\d+(?:\.\d+)?)")
+
+
+def main() -> None:
+    parser = argparse.ArgumentParser()
+    parser.add_argument("input", type=Path)
+    parser.add_argument("output", type=Path)
+    parser.add_argument("--factor", type=float, default=4.0)
+    args = parser.parse_args()
+
+    source = args.input.read_text()
+    original = [float(match.group(2)) for match in CLEARANCE.finditer(source)]
+    if not original:
+        raise RuntimeError(f"No clearance rules found in {args.input}")
+
+    def scale(match: re.Match[str]) -> str:
+        value = float(match.group(2)) * args.factor
+        rendered = str(int(value)) if value.is_integer() else f"{value:g}"
+        return match.group(1) + rendered
+
+    converted, count = CLEARANCE.subn(scale, source)
+    scaled = [float(match.group(2)) for match in CLEARANCE.finditer(converted)]
+    assert count == len(original) == len(scaled)
+    assert all(after == before * args.factor
+               for before, after in zip(original, scaled, strict=True))
+    # A conversion must never touch the board geometry or trace-width rules.
+    assert source.count("(width ") == converted.count("(width ")
+    assert source.count("(polygon ") == converted.count("(polygon ")
+    args.output.write_text(converted)
+    print(f"Scaled {count} clearance rules by {args.factor:g}x")
+    print(f"Saved {args.output}")
+
+
+if __name__ == "__main__":
+    main()