Entropy comes from FPGA ring oscillators whose sampled timing jitter is XOR-combined into output bits, with no pseudo-random post-processing. A SAMD21 serves the results over USB, and over HTTP on its own WiFi access point when running without a computer (stationary mode on a charger).
- 4 independent generators × 90 ring oscillators. Each generator XORs its rings every 120 MHz clock (spatial) and then several consecutive bits (temporal, default 5): about 24 Mbps per generator.
- Separate stream per generator, plus a combined stream of all healthy generators
- On-device health tests per generator: NIST SP 800-90B repetition count and adaptive proportion, plus a dead-ring monitor
- Live statistics per trial: bias, z-score, random walk and lag-1 autocorrelation, with rolling and cumulative windows
- Configurable random-walk / majority-vote bias amplifier on a bias path and an autocorrelation path, with sub-trial voting
- Von Neumann extractor that can be toggled on the stream, statistics and amplifier paths
- Raw ring captures and frequency measurement for characterization
-`arduino/libraries/`: `StrixFPGA` (FPGA boot, SPI access, embedded FPGA image), `VidorBoot` (vendored subset of Arduino's VidorPeripherals) and `WiFiNINA` (Arduino's library, patched to drive the WiFi module through the FPGA's pin pass-through)
The toolchain is managed by [devbox](https://www.jetify.com/devbox): `arduino-cli`, Intel Quartus Prime Lite (Cyclone 10 LP only, through a Nix flake in `nix/`), Icarus Verilog, Python and Rust.
Serial access requires membership in the `dialout` group. If a firmware leaves the board unable to stay on USB, enter the bootloader: hold reset while plugging in, release, then tap reset once quickly. For characterization, flash the capture tool with `devbox run upload-capture` and use `devbox run jitter <freq|rings|sweep|output|health|stats|amp|pairs>`. `devbox run onod-build` builds the onod3000 test suite used by `jitter output` and `api-check`.
