The simulator I wished existed when I was debugging firmware on a plane.

Why this exists

Embedded development has a productivity ceiling that's been stuck for two decades: you can only iterate as fast as you can flash, watch, and recover a dev board. Bad code bricks the board. Good code can't be regression-tested without a HIL bench no one has the time or budget to build.

Meanwhile, AI coding agents are getting good enough to write embedded firmware — but they need a sandbox where their first attempt can't toast a $40 ESP32 or short out your power-supply circuit. Browser-based Wokwi is the closest precedent; it's not open, not deterministic, and not built for CI.

LabWired is the open simulator I wanted: same firmware binary on hardware and in the browser, deterministic enough for CI regression tests, and exposed via an MCP server so coding agents can verify their firmware before it ever touches silicon.

What's actually in the box

• Three CPU backends — ARM Cortex-M (M0+/M3/M4/M4F/M33), RISC-V RV32I/RV32A, and Xtensa LX6/LX7 (ESP32 / ESP32-S3 with dual-core). Real instruction-level emulators, not stubs. ~5,700 lines of Rust per backend.
• Peripheral models — STM32 F1/F4/L4/H5/F407 peripherals (UART, SPI, I²C, GPIO, RCC, SysTick, EXTI, DMA, more), ESP32-S3 GPIO / I²C / VSPI / interrupt matrix / SYSTIMER, plus virtual sensors (BME280, MPU-6050, ADXL345, MAX31855, NEO-6M GPS) and displays (SSD1306, SSD1680, UC8151D, ILI9341).
• Hardware oracle harness — a real test harness that flashes firmware to physical silicon via OpenOCD/GDB and diffs the capture against the sim trace. Wired to a NUCLEO-H563ZI and ESP32-S3-Zero on the build runner.
• Production-grade debug — native GDB Remote Serial Protocol stub plus a VS Code Debug Adapter Protocol server. Breakpoints, conditional breakpoints, data watchpoints, expression evaluation, source-line correlation.
• MCP server for AI coding agents — exposes simulate, validate_system, list_boards, and 8 more tools so an agent can iterate on firmware without ever needing the physical board.

Two markets, same wedge

The same simulation kernel serves two go-to-market motions:

• Embedded teams replacing HIL benches. Drop a GitHub Action into your repo, regression-test every firmware change against a deterministic sim instead of a $5k+ rack of dev boards. Pricing on /ci →
• AI coding agents needing a hardware sandbox. Verify generated firmware in a fast, deterministic environment before the first flash. MCP server ships with the open-source core.

Building in the open

Simulator core is MIT-licensed on GitHub. Release cadence is visible in CHANGELOG.md — 15 releases between February and May 2026, including ESP32-S3 dual-core support and the hardware-oracle harness. Issue tracker is public. Contributions welcome.

Get in touch

Working on something LabWired could help with — firmware CI, an AI coding agent that needs a sandbox, embedded education? I'd like to hear about it.

andrii@shylenko.com · Book 30 minutes · @w1ne on GitHub