Avr8Sharp

Avr8Sharp is a high-performance emulator for the AVR 8-bit microcontroller family, written entirely in modern C# (.NET 10). It runs real, unmodified Arduino and AVR firmware and is designed as a deterministic firmware testkit — for example, validating the output of the PyMCU compiler in CI.

It is a C# port and re-imagination of avr8js by Uri Shaked, with additional accuracy fixes and .NET-specific optimizations.

dotnet add package Avr8Sharp
dotnet add package Avr8Sharp.TestKit   # fluent harness for firmware tests

using Avr8Sharp.TestKit.Boards;

var sim = new ArduinoUnoSimulation()
    .WithHex(File.ReadAllText("sketch.hex"));

sim.RunMilliseconds(500);

sim.PortB.Should().HavePinHigh(5);    // digital pin 13 (LED_BUILTIN)
sim.Serial.Should().Contain("Hello");

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Why Avr8Sharp

Real firmware, unmodified

Executes precompiled AVR firmware — Arduino sketches, avr-gcc output, PyMCU-generated binaries — without patches or shims.

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.

Accurate flags

Half-carry, overflow, sign, and carry flags match the ATmega datasheet for all supported instructions. Accuracy bugs inherited from the parent avr8js repo have been corrected.

Board presets

ArduinoUnoSimulation, ArduinoMegaSimulation, and ATtiny85Simulation wire up all peripherals automatically — ports, timers, serial, EEPROM, ready to use.

AOT-friendly

The core library is trimmable and NativeAOT-compatible — embed it in mobile apps, CLI tools, or circuit simulators.

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How it compares to avr8js

	avr8js	Avr8Sharp
Language	TypeScript	C# (.NET 10)
Half-carry accuracy	Several bugs	Fixed (ADC, CPI, NEG, SBIW, SUBI)
Test harness	—	Fluent TestKit + assertions
Board presets	—	Uno, Mega 2560, ATtiny85
CI guardrails	—	Bounded runs, health assertions
Deterministic clock	Yes	Yes
AOT / trimming	n/a	Yes

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