Add Freerouting autoroute script

- autoroute.sh: Downloads and runs Freerouting in batch mode
- Updated README with complete PCB layout workflow
- Script handles DSN→SES conversion automatically

Usage: Export DSN from KiCad, run ./autoroute.sh, import SES

README.md

@@ -62,6 +62,25 @@ SN-L00/
 
 Full BOM with LCSC part numbers in [hardware/BOM.md](hardware/BOM.md).
 
+### PCB Layout (KiCad 8)
+
+1. Open `hardware/kicad/SN-L00.kicad_pro`
+2. Update PCB from schematic: **Tools → Update PCB from Schematic** (F8)
+3. Place components using the script:
+   ```python
+   # In KiCad Scripting Console (Tools → Scripting Console)
+   exec(open('scripts/place_components.py').read())
+   ```
+4. Autoroute using Freerouting:
+   ```bash
+   # Export DSN from KiCad: File → Export → Specctra DSN
+   ./hardware/kicad/scripts/autoroute.sh
+   # Import SES in KiCad: File → Import → Specctra Session
+   ```
+5. Fill zones: Press **B**
+6. Run DRC: **Inspect → Design Rules Checker**
+7. Export Gerbers: **File → Fabrication Outputs → Gerbers**
+
 ### Manufacturing
 
 - PCB: 2-layer, 28×100mm

hardware/kicad/scripts/autoroute.sh

@@ -0,0 +1,111 @@
+#!/bin/bash
+#
+# SN-L00 Autorouting Script using Freerouting
+#
+# Usage:
+#   ./autoroute.sh                    # Uses default paths
+#   ./autoroute.sh input.dsn          # Custom input file
+#   ./autoroute.sh input.dsn output.ses
+#
+# Prerequisites:
+#   1. Export DSN from KiCad: File → Export → Specctra DSN
+#   2. Java runtime installed
+#
+# After running:
+#   Import the .ses file in KiCad: File → Import → Specctra Session
+#
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_DIR="$(dirname "$SCRIPT_DIR")"
+FREEROUTING_JAR="${FREEROUTING_JAR:-/tmp/freerouting.jar}"
+FREEROUTING_URL="https://github.com/freerouting/freerouting/releases/download/v2.0.1/freerouting-2.0.1.jar"
+
+# Default input/output paths
+DSN_FILE="${1:-$PROJECT_DIR/SN-L00.dsn}"
+SES_FILE="${2:-${DSN_FILE%.dsn}.ses}"
+
+# Colors for output
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+NC='\033[0m' # No Color
+
+echo -e "${GREEN}SN-L00 Autorouting Script${NC}"
+echo "=========================================="
+
+# Check for Java
+if ! command -v java &> /dev/null; then
+    echo -e "${RED}Error: Java is not installed${NC}"
+    echo "Install with: sudo apt install default-jre"
+    exit 1
+fi
+
+# Download Freerouting if not present
+if [[ ! -f "$FREEROUTING_JAR" ]]; then
+    echo -e "${YELLOW}Downloading Freerouting...${NC}"
+    curl -sL -o "$FREEROUTING_JAR" "$FREEROUTING_URL"
+    echo -e "${GREEN}Downloaded to $FREEROUTING_JAR${NC}"
+fi
+
+# Check for input DSN file
+if [[ ! -f "$DSN_FILE" ]]; then
+    echo -e "${RED}Error: DSN file not found: $DSN_FILE${NC}"
+    echo ""
+    echo "To create the DSN file:"
+    echo "  1. Open SN-L00.kicad_pcb in KiCad"
+    echo "  2. File → Export → Specctra DSN"
+    echo "  3. Save as: $DSN_FILE"
+    echo ""
+    echo "Then run this script again."
+    exit 1
+fi
+
+echo "Input:  $DSN_FILE"
+echo "Output: $SES_FILE"
+echo ""
+
+# Run Freerouting in batch mode
+echo -e "${YELLOW}Running Freerouting (this may take a while)...${NC}"
+echo ""
+
+# Freerouting command-line options:
+#   -de <file>  : Design input file (DSN)
+#   -do <file>  : Design output file (SES)
+#   -mp <passes>: Max routing passes (default: unlimited)
+#   -mt <mins>  : Max time in minutes (optional)
+#   -oit        : Order of routing: inside to outside
+#   -us         : Use saved rules from DSN file
+
+java -jar "$FREEROUTING_JAR" \
+    -de "$DSN_FILE" \
+    -do "$SES_FILE" \
+    -mp 100 \
+    -oit \
+    2>&1 | while IFS= read -r line; do
+        # Filter and display progress
+        if [[ "$line" == *"Pass"* ]] || [[ "$line" == *"route"* ]] || [[ "$line" == *"via"* ]]; then
+            echo "  $line"
+        fi
+    done
+
+# Check if output was created
+if [[ -f "$SES_FILE" ]]; then
+    echo ""
+    echo -e "${GREEN}Routing complete!${NC}"
+    echo ""
+    echo "Output saved to: $SES_FILE"
+    echo ""
+    echo "Next steps:"
+    echo "  1. Open SN-L00.kicad_pcb in KiCad"
+    echo "  2. File → Import → Specctra Session"
+    echo "  3. Select: $SES_FILE"
+    echo "  4. Press 'B' to fill copper zones"
+    echo "  5. Run DRC: Inspect → Design Rules Checker"
+else
+    echo -e "${RED}Error: Routing failed - no output file created${NC}"
+    echo "Try running Freerouting interactively:"
+    echo "  java -jar $FREEROUTING_JAR"
+    exit 1
+fi