nearxos/kicad-mcp-server
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

fix: change snap_to_grid default grid from 2.54mm to 1.27mm (50 mil)

Browse Source 
Half of all valid KiCAD schematic pin positions are on the 50-mil
(1.27mm) grid but not the 100-mil (2.54mm) grid — e.g. 26.67mm = 21 ×
1.27mm. Snapping to 2.54mm displaced those coordinates by 1.27mm,
moving labels off their pins and increasing floating-label count.

KiCAD source confirms: DEFAULT_CONNECTION_GRID_MILS = 50 and the ERC
off-grid check uses exact integer modulo against this value, so any
displacement breaks connectivity unconditionally.

Also update the kicad-source absolute path in CLAUDE.md.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
Eugene Mikhantyev
2026-04-12 18:10:55 +01:00
parent 33a2118960
commit ba09fc4e0f
5 changed files with 101 additions and 12 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
python/commands/schematic_snap.py
View File

@@ -4,9 +4,18 @@ Snap-to-grid tool for KiCAD schematics.
Snaps wire endpoints, junction positions, net labels, and optionally component
positions to the nearest grid point. Modifies the schematic file in place.
The standard KiCAD eeschema grid is 2.54 mm (0.1 inch). Off-grid coordinates
cause wires that appear visually connected to fail ERC connectivity checks
because KiCAD uses exact integer (IU) matching internally.
The standard KiCAD schematic grid is 50 mil (1.27 mm). Component pins are
placed at multiples of 1.27 mm relative to the symbol origin, so absolute pin
coordinates end up as odd multiples of 1.27 mm (e.g. 26.67 mm = 21 × 1.27 mm).
These are valid on-grid positions that must not be moved.
The coarser 2.54 mm (100-mil) grid is a common mistake: exactly half of all
valid 1.27 mm positions are not multiples of 2.54 mm and would be displaced by
1.27 mm — moving labels or wire endpoints off their pins and breaking
connectivity.
Off-grid coordinates cause wires that appear visually connected to fail ERC
connectivity checks because KiCAD uses exact integer (IU) matching internally.
"""
import logging
@@ -18,7 +27,7 @@ from sexpdata import Symbol
logger = logging.getLogger("kicad_interface")
_DEFAULT_GRID_MM: float = 2.54
_DEFAULT_GRID_MM: float = 1.27
# Element type names exposed in the public API
_VALID_ELEMENTS = frozenset({"wires", "junctions", "labels", "components"})
@@ -91,7 +100,10 @@ def snap_to_grid(
Args:
schematic_path: Path to the ``.kicad_sch`` file.
grid_size: Grid spacing in mm (default 2.54 mm = 0.1 inch).
grid_size: Grid spacing in mm (default 1.27 mm = 50 mil).
Do NOT use 2.54 mm — half of all valid KiCAD pin
positions fall between 2.54 mm grid lines and would
be displaced 1.27 mm, breaking connectivity.
elements: List of element types to snap. Valid values:
``"wires"``, ``"junctions"``, ``"labels"``,
``"components"``. Defaults to