Skip to content

CLAUDE.md

Latest commit

 

History

History
107 lines (70 loc) · 4.03 KB

CLAUDE.md

File metadata and controls

107 lines (70 loc) · 4.03 KB

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project Overview

OCoil is an OCaml command-line tool for PCB design calculations with three main functions:

  1. Trace resistance calculation - Calculate electrical resistance of copper traces with temperature compensation
  2. Spiral coil resistance calculation - Calculate total resistance of multi-turn spiral coils
  3. KiCad footprint generation - Generate .kicad_mod files for multi-layer spiral coil footprints

Build and Development Commands

Building

dune build

Running Commands

# Trace resistance calculation
dune exec -- bin/main.exe trace 0.01 -w 0.5mm -t 2oz --temp 85

# Spiral coil resistance calculation
dune exec -- bin/main.exe coil --pitch 0.6 --turns 2.5 --width 0.2 --round 6

# KiCad footprint generation
dune exec -- bin/main.exe kicad --pitch 0.64 --width 0.5 --clearance 0.14 --turns 5 --layers 3 --oval 13.9x6.22 --via-size 0.3/0.15 --output coil.kicad_mod

Testing

When testing the kicad command, don't specify the --output parameter. The footprint will be printed to the standard output.

Code Architecture

Multi-Command Structure

The tool uses cmdliner to provide three subcommands (trace, coil, kicad) from a single executable in bin/main.ml. Each subcommand has distinct argument parsing and delegates to library functions.

Library Organization (lib/)

trace.ml - Core physics calculations:

  • Copper resistivity constants and temperature coefficients
  • calculate_resistance - Implements R = ρL/A with temperature compensation
  • Unit conversion utilities for PCB industry standards (oz/ft², mils)

coil.ml - Spiral coil geometry and generation:

  • coil_shape sum type supporting Round, Square, Rectangular, and Oval geometries
  • generate_spiral_segments - Creates path segments for multi-layer coils with automatic layer mirroring
  • Transformation matrices for coordinate mirroring and rotation
  • Layer-aware segment generation with layer_segments grouping

kicad.ml - KiCad footprint serialization:

  • S-expression generation using sexplib0 with custom formatting functions
  • Complete KiCad footprint type system including pads, primitives, and metadata
  • generate_footprint - Converts coil segments to .kicad_mod format
  • Automatic via generation for even-numbered layers with configurable sizes
  • Layer assignment logic for multi-layer PCBs (F.Cu, In1.Cu, In2.Cu, In3.Cu, In4.Cu, B.Cu)

Key Design Patterns

Dimension Parsing: The dimension_converter in main.ml handles multiple unit formats (mm, mil, oz, um) with intelligent defaults, used across all subcommands for consistent UX.

Multi-Layer Coil Architecture:

  • Coils are generated per-layer with generate_spiral_segments_layer
  • Even layers (0, 2, 4...) get automatic via generation at segment endpoints
  • Odd layers get coordinate mirroring for optimal routing
  • Layer assignment follows PCB industry conventions

Footprint Generation Pipeline:

  1. Generate geometric path segments for each layer
  2. Convert segments to KiCad primitives (fp_line, fp_arc)
  3. Add pads, vias, properties, and metadata
  4. Serialize to S-expression format with custom formatting

Dependencies

  • OCaml + Dune - Core build system
  • Cmdliner - Type-safe command-line parsing
  • sexplib0 + ppx_sexp_conv - S-expression serialization for KiCad format
  • Uuidm - UUID generation for KiCad components

Unit Format Support

All dimensional inputs support flexible unit parsing:

Length/Width: 0.5mm, 20mil, 1.2 (mm default) Thickness: 35um, 1oz, 2oz (oz default)
Via Sizes: 0.3/0.15, 12mil/6mil, 0.4mm/8mil (copper/drill format)

Multi-Layer Coil Features

  • Supports 1-6 layer coils with automatic layer assignment
  • Even layers get thru-hole vias for inter-layer connections
  • Odd layers use coordinate mirroring for routing optimization
  • Configurable via sizes with separate copper and drill specifications
  • Automatic trace clearance and pitch calculations