AI-Assisted FPGA Development: Cursor IDE for Tang Nano 9K Projects

FPGA development has traditionally been a steep learning curve—wrestling with HDL syntax, peripheral datasheets, and synthesis quirks. But what if you could leverage AI to accelerate your workflow? This guide walks you through using Cursor IDE (Claude-powered code generation) for Tang Nano 9K development, with practical setup advice and hard-won pitfalls to avoid.

Why Cursor for FPGA?

Tang Nano 9K is an accessible FPGA board, but the toolchain (EDA Suite, Verilog, IP cores) demands deep domain knowledge. Cursor, built on Claude, excels at:

• Code generation: Writing synthesizable Verilog from natural language descriptions
• Peripheral integration: Generating boilerplate for HDMI, PSRAM, SPI with correct pin mappings
• Debugging: Analyzing error logs and suggesting fixes
• Documentation: Explaining complex HDL patterns

The caveat? You need domain knowledge to guide and validate AI output. This guide covers both.

---

Part 1: Setup

Prerequisites

• Tang Nano 9K board with USB programmer
• EDA Suite (Gowin IDE or command-line tools)
• Cursor IDE installed (free tier available)
• Verilog basics: Modules, always blocks, instantiation
• Tang Nano datasheets for pinouts and IP cores

Step 1: Install Cursor

1. Download from cursor.com
2. Launch and authenticate (free tier works for learning)
3. Create a project folder for your Tang Nano work

Step 2: Set Up Project Structure

Create a standard FPGA project layout with src/, constraints/, sim/, and docs/ directories.

Step 3: Create a Knowledge Base for Cursor

This is critical. Create a knowledge_base.md file with Tang Nano-specific details:

Pin Assignments:

• LED: IO_25 (active high)
• Button: IO_26 (active low)
• HDMI_CK: IO_17, HDMI_D0-D2: IO_18-20
• PSRAM_CLK: IO_35, PSRAM_CS: IO_36, PSRAM_MOSI: IO_37, PSRAM_MISO: IO_38

IP Cores:

• rPLL: Clock generation (VCO: 600MHz–3GHz)
• OSER10: 10:1 serializer for HDMI TMDS
• ELVDS_OBUF: Differential output buffer for HDMI
• BSRAM: Built-in SRAM (256K bits)
• SSRAM_CTRL: PSRAM controller (32MB external)

Common Mistakes:

• PSRAM slew rate must be HIGH (not FAST)
• PLL VCO max is 3GHz
• HDMI TMDS requires 10:1 serialization per lane

---

Part 2: Workflow Tips

Tip 1: Start with High-Level Prompts

Instead of "generate HDMI code," give full context:

Good: "I'm building HDMI output on Tang Nano 9K with 50MHz input clock. Use rPLL for 74.25MHz pixel clock and OSER10 for TMDS. Pins: HDMI_CK=IO_17, HDMI_D0=IO_18. Generate top-level Verilog module."

Poor: "Generate HDMI code."

Tip 2: Validate Against Datasheets

Cursor generates plausible Verilog, but always cross-check:

• Clock domains and timing constraints
• Pin voltage levels (3.3V for Tang Nano logic)
• IP core parameter ranges against official specs

Tip 3: Iterative Refinement with Tests

Ask Cursor to generate both RTL and testbenches. This catches logic errors early before synthesis.

Tip 4: Leverage Diff View

Use Cursor's inline diff feature to review changes line-by-line before accepting modifications.

Tip 5: Debug Synthesis Errors Together

Paste full error logs into Cursor with context. It can identify missing IP instantiations, parameter mismatches, or constraint issues.

---

Part 3: Pitfalls to Avoid

Pitfall 1: Over-Trusting AI for Pin Assignments

Always reference pins.cst constraints and cross-check against datasheets before synthesis.

Pitfall 2: Ignoring Timing Constraints

Ask Cursor to generate timing constraints (.cst) alongside HDL. Test timing closure at your target frequency (e.g., 74.25MHz for HDMI).

Pitfall 3: Mixing AI and Manual Code Without Version Control

Use git with meaningful commits. Comment all AI-generated sections clearly in code.

Pitfall 4: Not Keeping Synthesis Logs

Save every synthesis log with timestamps. Ask Cursor to analyze old logs for patterns when debugging recurring issues.

Pitfall 5: Asking for Too Much at Once

Break designs into modules: HDMI driver → PSRAM controller → top-level glue. Test each in isolation first.

Pitfall 6: Forgetting Power and Thermal Constraints

Include power budgets in prompts. Ask Cursor about clock gating and low-power techniques to avoid overheating.

---

Part 4: Real-World Example

Here's a workflow for building an LED blinker with PLL-generated clock:

Step 1: Write a Detailed Prompt

Specify input clocks, output frequency, pin assignments, and IP requirements.

Step 2: Review Generated Code

Verify PLL parameters are within spec, divider math is correct, and IO voltage levels are appropriate.

Step 3: Synthesize and Test

Run gowin_pack and check for errors. If synthesis fails, paste the error log back to Cursor.

Step 4: Program and Observe

Upload to Tang Nano and verify the LED blinks at your target frequency.

---

Key Takeaways

1. Build a knowledge base upfront (pins, IP specs, common mistakes)
2. Prompt iteratively with context and constraints
3. Validate relentlessly against datasheets and synthesis logs
4. Version control your work and mark AI-generated sections
5. Break problems into modules and test incrementally

With this workflow, you'll accelerate from struggling with Verilog syntax to rapidly prototyping complex designs on Tang Nano 9K.

---

Tools & Resources

• Cursor IDE: AI-assisted code editing
• Gowin EDA: Synthesis and place-and-route
• GTKWave: Waveform viewing
• Tang Nano Docs: Pinouts, IP cores, examples

---

Conclusion

Cursor is a powerful multiplier for FPGA development—if you know how to guide it. The key is building domain knowledge upfront, prompting with context, validating against specifications, maintaining version control, and breaking problems into testable modules.

Happy building! 🚀

What's your biggest FPGA pain point? Share in the comments—I'd love to hear how Cursor could help you solve it faster.