RISC-V bare metal compiler

Compile to bare metal.

A systems language for RISC-V embedded. No LLVM, no runtime, no external toolchain. Source code goes in, firmware comes out.

See the code Learn more

terminal

Debugger

Scrub through execution.

Every cycle recorded. Drag the timeline to see registers change and GPIO pins toggle.

x0 0x00000000 ra 0x00000000 sp 0x3fce4000 gp 0x00000000

tp 0x00000000 t0 0x00000000 t1 0x00000000 t2 0x00000000

s0 0x00000000 s1 0x00000000 a0 0x00000000 a1 0x00000000

a2 0x00000000 a3 0x00000000 a4 0x00000000 a5 0x00000000

a6 0x00000000 a7 0x00000000 s2 0x00000000 s3 0x00000000

s4 0x00000000 s5 0x00000000 s6 0x00000000 s7 0x00000000

s8 0x00000000 s9 0x00000000 s10 0x00000000 s11 0x00000000

t3 0x00000000 t4 0x00000000 t5 0x00000000 t6 0x00000000

GPIO pins

Features

What it actually does.

No roadmap promises. This is what works right now.

No LLVM

Straight to machine code. 8 optimizer passes, RV32C compression. The whole compiler is about 10K lines of Rust.

Peripheral ownership

Claim a GPIO pin twice and the compiler yells at you. Ownership is tracked at the type level, not at runtime.

Error unions + try

Functions return values or errors. try unwraps or propagates. No exceptions, no hidden control flow.

Time-travel debugger

Every CPU cycle gets recorded. Scrub backward through execution and see exactly what wrote that register.

Built-in emulator

RV32IM emulator with MMIO logging baked in. Write code, run it, see GPIO toggles. No hardware needed to start.

Agent-friendly

JSON errors, a check command, deterministic output. Built so AI agents can compile and verify without hand-holding.

Syntax

Looks like Rust. Compiles to bare metal.

If you can read Rust, you can read Kov. Board definitions are part of the grammar.

// board definition is the language
board esp32c3 {
    gpio: GPIO @ 0x6000_4000,
    uart: UART @ 0x6000_0000,
    clock: 160_000_000,
}

fn main(b: &mut esp32c3) {
    let led = b.gpio.pin(2, .output);
    let tx = b.uart.open(115200);

    loop {
        led.high();
        delay_ms(500);
        led.low();
        delay_ms(500);
        tx.write("blink\n");
    }
}

Comparison

Honest comparison.

	C	Rust	Kov
LLVM required	Yes	Yes	No
Peripheral safety	None	Runtime	Compile-time
Stack overflow	Silent	Panic	Compile error
WCET analysis	External tool	External tool	Built-in
Interrupt safety	Manual	RTIC macro	Static analysis
Runs in browser	No	No	Yes (WASM)
Compile time	2–10s	10–60s	<1ms

Built from scratch. All open source.

One person, Rust, no dependencies. Compiler, emulator, optimizer, and now a browser playground.

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