GF-Pinmap — Board-Aware Pin Mapping

Workflow

1. Identify board — Check .gateflow/project.yaml target.board or ask user
2. Check curated database first:

   ls ${CLAUDE_PLUGIN_ROOT}/boards/<board>/board.yaml 2>/dev/null
   

3. If board found: Read board.yaml, generate constraint file
4. If board NOT found: Web search as fallback, require user confirmation
5. Cross-reference generated constraints with RTL port list
6. Output constraint file in correct format for target FPGA

Curated Board Flow

1. Read boards/<board>/board.yaml for pin data
2. Read boards/<board>/constraints.* for template
3. Map RTL ports → board pins based on user's peripheral selection
4. Generate complete constraint file with:
   • PACKAGE_PIN
   • IOSTANDARD (from board.yaml)
   • DRIVE strength (default 12mA for outputs)
   • SLEW rate (default SLOW)
   • PULLUP for active-low signals

Web Search Fallback

Only when board is NOT in curated database:

1. Search: "<board name>" constraint file site:github.com
2. Search: "<board name>" pinout .xdc OR .pcf OR .lpf
3. Present findings to user with WARNING:

   Found constraint data for <board> via web search.
   Source: <url>
   
   WARNING: This pin data has NOT been verified against the official
   board documentation. Incorrect pin assignments can damage hardware.
   
   Please review before applying:
   [show pin assignments]
   
   Apply these constraints? [Y/n]
   

4. NEVER auto-apply web-searched data

Safety

• Never guess pin assignments
• Always include IOSTANDARD (missing = synthesis error or hardware damage)
• Check voltage bank compatibility
• Warn if mixing I/O standards in the same bank
• Active-low signals get PULLUP

GATEFLOW-RESULT Format

---GATEFLOW-RESULT---
STATUS: PASS | FAIL | ERROR
FORMAT: xdc | pcf | lpf | cst
BOARD: <board name>
PINS_MAPPED: <count>
PINS_UNMAPPED: <count>
FILE: <constraint file path>
DETAILS: <summary>
---END-GATEFLOW-RESULT---

I/O Standard Reference

IOSTANDARD	Voltage	Max Speed	Typical Use
LVCMOS33	3.3V	~100 MHz	GPIO, LEDs, UART, SPI
LVCMOS25	2.5V	~150 MHz	Mixed-voltage
LVCMOS18	1.8V	~200 MHz	Modern peripherals
LVDS_25	2.5V diff	~1 Gbps	High-speed serial
SSTL15	1.5V	~800 MHz	DDR3
TMDS_33	3.3V	~750 Mbps	HDMI/DVI

Common Pin Mapping Mistakes

1. Missing IOSTANDARD -> Defaults may damage hardware. Always specify.
2. Mixing I/O standards in same bank -> All pins in a bank share VCCO.
3. Floating inputs -> Add PULLUP/PULLDOWN to unused inputs.
4. No termination on high-speed -> Use ODT for DDR, 100-ohm for LVDS.
5. Wrong DRIVE strength -> 4mA for LEDs, 8-12mA for SPI.
6. Forgetting create_clock -> No timing analysis without it.

PMOD Mapping Patterns

Standard PMOD pinout: pins 1-4 (top row I/O), 5 (GND), 6 (VCC), 7-10 (bottom row I/O), 11 (GND), 12 (VCC).

PMOD Type	Pin 1	Pin 2	Pin 3	Pin 4
Type 2 (SPI)	CS_N	MOSI	MISO	SCLK
Type 3 (UART)	CTS	TXD	RXD	RTS
Type 6 (I2C)	SCL	SDA	INT_N	RST_N