NuttX (contributor / in-tree workflow)

Looking for the user-facing path? This page covers building nano-ros’s own NuttX examples on QEMU from this repository. If you’re integrating nano-ros into YOUR NuttX app at apps/external/nano-ros/, see Integration: NuttX external app instead.

nano-ros runs on NuttX, targeting QEMU ARM virt (Cortex-A7 + virtio-net). NuttX provides POSIX-compatible BSD sockets, which makes it the most straightforward RTOS port – zenoh-pico uses the same socket API as on Linux.

Overview

The NuttX platform uses:

• NuttX RTOS – POSIX-compliant real-time OS with BSD socket support
• BSD sockets – standard socket API provided by NuttX’s network stack
• zenoh-pico – Zenoh transport over NuttX sockets (same code path as POSIX)
• virtio-net – NuttX built-in Ethernet driver (no custom driver needed)

Board crate: nros-board-nuttx-qemu (in packages/boards/) — ONE crate serves both QEMU NuttX boards, arm virt and rv-virt. Everything that differs between them is data (a defconfig, a toolchain file, a target triple); nothing in the Rust or C sources is arch-conditional.

Why NuttX Is Simpler Than FreeRTOS

NuttX is the simplest RTOS platform to port because of its strong POSIX compliance (POSIX.1-2008: pthreads, BSD sockets, select(), clock_gettime()):

Because NuttX supports Rust std, examples use standard fn main() entry points and println! – no semihosting or custom panic handlers needed.

Setup

nros setup qemu-arm-nuttx provisions everything this board needs — the NuttX cross-compiler, qemu-system-arm, the NuttX source tree, and the RMW host daemon — into the shared store at ~/.nros/sdk. No hand-installed cross-toolchain and no ROS 2 install required.

Build the in-tree nros CLI (Phase 218), then provision the board (--rmw defaults to zenoh):

./scripts/bootstrap.sh      # builds packages/cli/target/release/nros
source ./activate.sh        # OR: direnv allow / source ./activate.fish
nros setup qemu-arm-nuttx --rmw zenoh

As a contributor, just setup nuttx remains available and now delegates to nros setup qemu-arm-nuttx for the toolchain/SDK provisioning while also staging the external apps.

The NuttX sources land in third-party/nuttx/nuttx/ and third-party/nuttx/nuttx-apps/. Override the paths with environment variables if your sources are elsewhere:

Prerequisites

The nros setup qemu-arm-nuttx step above provisions the qemu-system-arm emulator and the arm-none-eabi-gcc cross-compiler used for NuttX kernel compilation. The one host-side tool you still supply yourself:

• Rust nightly toolchain (NuttX targets are Tier 3, require -Z build-std)

Building

Contributors: the in-tree build lanes for this platform are in Per-Platform Contributor Lanes.

The examples link against NuttX’s POSIX layer, which provides sockets, pthreads, and standard I/O.

Available Examples

All examples are in examples/qemu-arm-nuttx/rust/:

RISC-V (rv-virt, riscv32)

The same NuttX path also runs on QEMU’s RISC-V rv-virt board (rv32imac, riscv32imac-unknown-nuttx-elf), proving the provisioning path is arch-agnostic. Provision and build with:

nros setup qemu-riscv-nuttx --rmw zenoh

Contributors: the in-tree RISC-V fixture build lanes are in Per-Platform Contributor Lanes.

Board crate: nros-board-nuttx-qemu (in packages/boards/) — the same crate as the arm board above, selected by deploy = "nuttx-riscv", which picks the rv-virt [[board]] entry of its nros-board.toml (riscv toolchain, riscv defconfig, riscv32imac-unknown-nuttx-elf). The C pub/sub pair is exercised end-to-end under qemu-system-riscv32, and Rust / C / C++ realtime-tiers workspace runtime lanes cover the multi-tier scheduling path on this board.

Testing

Contributors: the in-tree test lanes for this platform are in Per-Platform Contributor Lanes.

Tests run under qemu-system-arm -M virt with TAP networking. Each QEMU instance connects to the host bridge (br-qemu) via TAP devices for zenohd communication. The test infrastructure builds a NuttX kernel image with the example app embedded, boots it in QEMU, and verifies message exchange.

Network Configuration

NuttX QEMU instances use the same IP scheme as other QEMU board crates:

Architecture

Board Crate

The nros-board-nuttx-qemu board crate follows the standard Config / run() pattern documented in the Custom Board Package guide. It provides network and node configuration presets (talker(), listener(), server(), client()).

Unlike bare-metal and FreeRTOS board crates, there is no custom hardware initialization, no network stack setup, and no task creation. NuttX’s kernel boots the hardware, initializes virtio-net, and starts the application before main() runs. Because NuttX supports Rust std, examples use standard fn main() entry points.

NuttX Defconfig

The QEMU board configuration lives in packages/boards/nros-board-nuttx-qemu/nuttx-config/arm/defconfig (the rv-virt one sits beside it under riscv/) and enables:

• CONFIG_NET – networking subsystem
• CONFIG_NET_TCP / CONFIG_NET_UDP – TCP/UDP protocols
• CONFIG_DRIVERS_VIRTIO + CONFIG_DRIVERS_VIRTIO_NET – virtio Ethernet
• CONFIG_PTHREAD_MUTEX_TYPES – POSIX mutex types (for zenoh-pico)
• CONFIG_DEV_URANDOM – /dev/urandom for session ID generation
• CONFIG_DEFAULT_TASK_STACKSIZE=8192 – adequate stack for nros apps
• CONFIG_BUILD_FLAT – flat memory model (no MMU protection)

Status

NuttX platform support is complete: feature flags, build integration, six Rust examples, E2E network tests, and documentation.