eda-schematics

EDA Schematics Skill

Create and wire schematics for electronics projects.

Auto-Activation Triggers

This skill activates when:

• User asks to "create schematic", "add component", "wire"
• User is working with .kicad_sch files
• User asks about net names, connections, or ERC
• Project has component selections but no schematic
• User mentions schematic organization or sheets

Context Requirements

Requires:

• docs/component-selections.md - Selected components with LCSC numbers
• docs/design-constraints.json - Project constraints
• datasheets/ - Component datasheets for reference circuits

Produces:

• hardware/*.kicad_sch - KiCad schematic file(s)
• docs/schematic-status.md - Status and progress tracking

Workflow

1. Load Context

@docs/design-constraints.json
@docs/component-selections.md
@datasheets/ (relevant datasheets)

From design-constraints.json, extract:

• power.topology - LDO vs buck affects schematic complexity
• power.rails[] - All voltage rails to implement
• board.layers - 2-layer = simpler designs, 4+ = can be more complex
• thermal.budget - Identify hot components for grouping
• dfmTargets.assembly - Package sizes must match

1.5. Validate Readiness

Before starting schematic:

• All required components selected in component-selections.md?
• MCU selected with known pinout?
• Voltage regulators selected?
• Critical passives (decoupling values) defined?
• Datasheets downloaded for reference circuits?

If not, suggest running /eda-source [role] first.

2. Plan Sheet Organization

See reference/SCHEMATIC-HIERARCHY-DECISION.md for detailed guidance.

Based on complexity, organize into sheets:

Simple design (1-2 sheets):

• Sheet 1: Everything

Medium design (3-4 sheets):

• Sheet 1: Power (input, regulators)
• Sheet 2: MCU and core logic
• Sheet 3: Interfaces and I/O

Complex design (5+ sheets):

• Sheet 1: Power input and protection
• Sheet 2: Voltage regulation
• Sheet 3: MCU and clock
• Sheet 4: Communication interfaces
• Sheet 5: Connectors and I/O
• Additional sheets as needed

3. Create Schematic Structure

• Create main schematic file
• Add hierarchical sheets if multi-sheet
• Set up page sizes and title blocks

4. Place Components (Per Sheet)

For each component:

1. Place symbol from library
2. Set reference designator
3. Set value
4. Add LCSC part number to properties
5. Position logically

Tool syntax:

mcp__kicad-sch__add_component schematic_path="/path/to/file.kicad_sch" lib_id="EDA-MCP:SymbolName" reference="U1" value="10k" position=[100, 100]

• Use symbol_ref from library_fetch response (e.g., EDA-MCP:ESP32-C3)
• For standard parts, use KiCad libraries (e.g., Device:R, Device:C)
• Position uses grid-aligned coordinates (1.27mm grid)

Placement guidelines:

• Power flows top-to-bottom or left-to-right
• Signal flows left-to-right
• Group related components
• Leave space for wiring

5. Add Power Symbols

• Place VCC symbols for each rail
• Place GND symbols
• Use consistent power symbol naming

6. Wire Connections

Follow the reference circuits from datasheets:

1. Wire power connections first
2. Add decoupling capacitors to power pins
3. Wire critical signals (crystal, reset)
4. Wire communication buses
5. Wire remaining signals

Use net labels for:

• Inter-sheet connections
• Buses
• Avoiding wire crossing
• Named signals (for clarity)

7. Verify and Document

• Check all pins connected or marked NC
• Run ERC (electrical rules check)
• Document status

See reference/ERC-VIOLATIONS-GUIDE.md for fixing common ERC errors.

8. Pre-Layout Review

Before proceeding to layout, complete reference/SCHEMATIC-REVIEW-CHECKLIST.md:

• Power section verification
• Decoupling validation
• Interface protection check
• Test points present
• Net naming consistency
• Documentation complete

Net Naming Convention

See reference/NET-NAMING.md for complete conventions.

Quick reference:

Power:    VCC_3V3, VCC_5V, VBAT, GND, GNDA
Reset:    MCU_RESET, nRESET
SPI:      SPI1_MOSI, SPI1_MISO, SPI1_SCK, SPI1_CS
I2C:      I2C1_SDA, I2C1_SCL
UART:     UART1_TX, UART1_RX
GPIO:     LED_STATUS, BTN_USER, or GPIO_PA0

Output Format

schematic-status.md

# Schematic Status

Project: [name]
Updated: [date]

## Summary
- Total sheets: X
- Components placed: Y
- Wiring: Z% complete
- ERC: X errors, Y warnings

## Sheets

### Sheet 1: Power
- Status: Complete
- Components: U1 (regulator), C1-C4 (caps)
- Notes: ...

### Sheet 2: MCU
- Status: In Progress
- Components: U2 (MCU), Y1 (crystal), C5-C10
- Notes: Needs clock wiring

## ERC Issues
- [ ] Unconnected pin on U2.PA3 (intentional NC)
- [x] Missing power flag (fixed)

## Next Steps
- Complete MCU clock circuit
- Wire SPI bus to flash
- Run final ERC

Guidelines

• Always check datasheets for reference circuits
• Place decoupling caps within 3mm of IC power pins (in layout)
• Use net labels for any signal that crosses sheets
• Keep schematic readable - avoid wire spaghetti
• Add notes for non-obvious connections
• Mark intentionally unconnected pins with NC flag

Architecture Validation Warnings

Check these before proceeding to layout:

Condition	Warning
Buck converter selected but no inductor in schematic	Missing critical component
USB interface but no ESD protection	Add ESD diodes before layout
External connector but no protection	Add TVS/ESD on exposed signals
MCU with <100nF per VDD pin	Verify decoupling against datasheet
Crystal but no load cap calculation	Recalculate CL values
I2C bus but no pull-ups	Add pull-ups (4.7K-10K)
SPI CS lines floating	Add pull-ups to prevent glitches
Reset pin without RC debounce	Add debounce circuit

Reference Documents

Document	Purpose
reference/NET-NAMING.md	Net naming conventions
reference/SYMBOL-ORGANIZATION.md	Schematic layout patterns
reference/REFERENCE-CIRCUITS.md	Common circuit patterns
reference/SCHEMATIC-HIERARCHY-DECISION.md	Sheet organization guidance
reference/SCHEMATIC-REVIEW-CHECKLIST.md	Pre-layout validation
reference/ERC-VIOLATIONS-GUIDE.md	Fixing ERC errors

Next Steps

After schematic is complete:

1. Generate netlist
2. Run /eda-layout to begin PCB layout
3. Update design-constraints.json stage to "pcb"