RP2040Sharp

RP2040Sharp is a high-performance emulator for the Raspberry Pi RP2040 microcontroller, written entirely in modern C# (.NET 10). It runs real, unmodified RP2040 firmware — including MicroPython — and reaches an interactive REPL in ~3–4 s of simulated time (~460 MIPS on Apple Silicon).

Its headline use case is firmware integration testing in CI/CD: run your real firmware headlessly and assert on what it actually does — toggles a pin, prints over UART, echoes bytes — with runs that are deterministic and never hang. It’s how the PyMCU compiler validates its output on every push. It is a C# port and re-imagination of rp2040js by Uri Shaked.

dotnet add package RP2040Sharp.TestKit   # fluent firmware-testing harness

using RP2040.TestKit.Boards;       // PicoSimulation
using RP2040.TestKit.Extensions;   // .Should() for pins, UART, CPU

using var pico = new PicoSimulation(withUsbCdc: false);
pico.LoadFlash(File.ReadAllBytes("firmware.bin"));

// Run real firmware and assert on its behavior — bounded, deterministic, headless.
pico.RunUntilOutput(pico.Uart0, "ready", timeoutMs: 5_000).Should().BeTrue();
pico.Gpio[25].Should().BeHigh();
pico.Cpu.Should().NotHaveFaulted();

→ Start with the firmware integration testing guide.

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Why RP2040Sharp

Firmware testing in CI

A fluent TestKit to drive real firmware and assert on GPIO, UART, and CPU state — dotnet test, no hardware.

Firmware integration testing in CI

Deterministic by design

Time is driven by executed cycles, never by wall-clock. Runs are reproducible across machines — ideal for CI and compiler regression checks.

Never hangs in CI

Bounded execution: wedged or crashed firmware fails a test with a diagnostic reason instead of stalling the build.

Real firmware, unmodified

Boots the real RP2040 B1 BootROM and runs stock MicroPython/CircuitPython UF2 images — no patches, no shims.

GDB debugging

Attach arm-none-eabi-gdb over target remote :3333 — registers, memory, single-step, breakpoints.

Dual-core

Core 1 launches through the SIO FIFO multicore handshake (RP2040 §2.8.3); both cores advance in lock-step.

AOT-friendly

The core library is trimmable and NativeAOT-compatible — embed it anywhere.

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How it compares to rp2040js

	rp2040js	RP2040Sharp
Language	TypeScript	C# (.NET 10)
GDB stub	Yes	Yes
Dual-core	Partial	Yes (working handshake)
Test harness	—	Fluent TestKit + assertions
CI guardrails	—	Bounded runs, health assertions, headless runner
Deterministic clock	Yes	Yes
AOT / trimming	n/a	Yes

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