About This Tool
This tool is a browser-based simulator for running and verifying PIO assembly code on the
RP2040 (Raspberry Pi Pico) and RP2350 (Pico 2).
No installation needed — open the page and immediately inspect state machine behavior.
PIO is a small state machine that runs independently of the CPU, enabling timing-critical I/O
(I2S, WS2812, arbitrary serial protocols) without CPU intervention. Its unique concepts —
a compact instruction set, side-set, delay cycles, FIFOs — can be tricky to understand before
writing to hardware. This simulator helps by letting you step through code one instruction at a
time while observing internal state.
The assembler accepts Pico SDK pioasm-compatible syntax and supports all
instructions (jmp, wait, in, out,
push, pull, mov, irq, set),
side-set, .wrap / .wrap_target, delay cycles, and IN/OUT/SET pin
mapping. During execution it visualizes SM registers (X, Y, OSR, ISR, PC), TX/RX FIFOs,
GPIO 0-31 I/O state, timing chart, and IRQ flags in real time.
Pure client-side implementation — everything runs in your browser. Code and state never leave
your machine. Free to use for PIO program development, Pico SDK learning, and educational
demonstrations.