Firmware Generation Limits

TL;DR

• AI can generate C for embedded. It often gets the structure right and the hardware-specific details wrong.
• Timing, interrupts, register maps, and hardware quirks need human knowledge. AI doesn't have your datasheet.
• Use AI for boilerplate and structure. You own: correctness, safety, and certification.

Firmware is a different beast from application code. Deterministic timing, direct hardware access, interrupt handlers, and resource constraints. AI has been trained on plenty of embedded code. But it hasn't been trained on your board, your timing requirements, or your certification process. The gaps are where you add value.

What AI Gets Right

• C syntax and structure. Loops, functions, basic patterns.
• Common peripherals. UART, SPI, I2C. Generic init sequences. High-level flow.
• RTOS usage. FreeRTOS tasks, semaphores, queues. Patterns are learnable.
• Booting and main loop. Setup, loop, basic state machine. Predictable.

Where AI Fails

• Register-level accuracy. Wrong addresses, wrong bit positions. AI hallucinates register maps. You verify against the datasheet.
• Timing-critical code. Interrupt latency, deadline guarantees. AI doesn't know your constraints.
• Hardware quirks. Errata, workarounds, board-specific pull-ups. Domain knowledge.
• Memory layout. Stack size, heap, DMA buffers. AI suggests; you verify it fits.
• Certification. MISRA, DO-178, ISO 26262. AI doesn't follow the rules. You enforce them.
• Vendor-specific SDKs. Silicon vendor SDKs change. AI may suggest deprecated or wrong APIs.

The Verification Rule

Treat every AI-generated firmware snippet as unverified until you:

• Cross-check registers and addresses against the datasheet
• Verify timing and interrupt behavior
• Ensure memory usage fits the device
• Run static analysis (MISRA, etc.) if required

When AI Is Useful

• Scaffolding. Project structure, build files, boilerplate init.
• Refactoring. Renaming, extracting functions. Structural changes.
• Documentation. Comments, README. AI drafts; you verify accuracy.
• Debugging assistance. "Why might this crash?" AI suggests hypotheses; you validate.

When to Avoid AI

• Safety-critical paths. Brakes, medical, aviation. Human-written, human-reviewed.
• Timing-sensitive interrupt handlers. You know the deadline; AI doesn't.
• First-time bring-up. New hardware. You need the datasheet; AI doesn't have it.
• Certification-bound code. Formal process. AI output adds verification burden.

Do This Next

1. Generate one peripheral driver (e.g., SPI init) with AI. Compare to the datasheet and vendor HAL. List every discrepancy. That's your "AI firmware review" filter.
2. Create a context file for your hardware: MCU, clocks, peripherals, key registers. Use it when prompting. Better context = fewer hallucinations.