Arduino & PlatformIO

Build systems and IDEs for hobby and pro embedded — Arduino IDE 2.x, PlatformIO, Arduino-CLI, Arduino Cores.

The "I plug in a board and press Upload" toolchains. Less ceremony than ESP-IDF and embedded RTOSes, with broad coverage across MCU platforms. For Rust see Embedded Rust; for Python see MicroPython & CircuitPython.

Arduino — the IDE and CLI

★ Arduino IDE 2.x — open source (AGPLv3); Eclipse-Theia-based rewrite of the classic IDE. Modern editor (Monaco-grade), serial monitor, debugger panel, board / library manager. The default for first-time MCU programmers in 2026.
Arduino IDE 1.8.x — legacy; still works on older OSes, but 2.x is now the recommended path.
★ Arduino-CLI — official command-line arduino-cli for compile / upload / library / board management. Open source. The headless / CI-friendly path; pairs with any editor.
Arduino Lab for MicroPython — Arduino-branded MicroPython editor; smaller scope.
Arduino Cloud Editor — browser IDE; freemium, syncs to Arduino Cloud accounts. Closed source; convenient for ChromeOS / classroom.
Arduino Cloud (IoT Cloud) — hosted IoT backend (devices, dashboards, OTA, things). Free tier exists; closed source.

Cores are what teach the Arduino toolchain about a chip. Most modern ones are open source.

★ arduino-esp32 (Espressif) — official ESP32 core; ships every variant (classic / S2 / S3 / C3 / C6 / H2 / P4). Built on top of ESP-IDF, so you get IDF features in Arduino sketches. Apache 2.0.
★ ESP8266 core for Arduino — community-maintained; still active, still works.
arduino-pico (Earle Philhower) — ★ the de-facto third-party RP2040 / RP2350 Arduino core; broader and more mature than Arduino's official Mbed-based "Arduino Mbed OS RP2040" core.
Arduino Mbed OS RP2040 / Nano boards core — Arduino's official Pico/Nano ESP32 core; uses Mbed OS underneath. Fine, but arduino-pico is generally preferred for hobby use.
Arduino-STM32 (rogerclarkmelbourne) — older STM32 core; mostly superseded by STM32duino (the official ST-blessed core) in 2026.
STM32duino — official STM32 Arduino core; covers most STM32 lines.
Adafruit nRF52 / SAMD cores — Adafruit's forks of the official cores with extra board defs.
MegaCore / MightyCore / MiniCore (MCUdude) — community AVR cores adding chips not in the stock core.
MegaTinyCore / DxCore — modern AVR (tinyAVR / Dx) cores.

The "Arduino-CLI but better organized" choice. Cross-platform, multi-MCU, dependency-managed projects.

★ PlatformIO Core — open source (Apache 2.0); CLI / build system supporting 1300+ boards across ESP / STM32 / nRF / RP / AVR / SAMD / Renesas / RISC-V. Reads platformio.ini. The professional default for non-trivial Arduino-style projects.
★ PlatformIO IDE for VS Code — free VS Code extension; the standard way to use PlatformIO. Project explorer, debugger UI, library registry, library deps inspector. Works on any OS.
PlatformIO IDE for CLion / Eclipse / Atom — older / less-maintained editor wrappers.
PlatformIO Registry — built-in package registry for libraries, platforms, tools, frameworks.
PlatformIO Remote (PIO Remote) — paid / commercial tier for remote build / upload.
PlatformIO Labs — paid commercial offerings (Plus / Enterprise: more registry quotas, advanced static analyzer integrations).

What platformio.ini gets you over Arduino IDE:

Real dependency pinning (lib_deps = ottowinter/ESPAsyncWebServer-esphome @ ^3.1.0).
Multiple build environments in one project ([env:esp32-s3], [env:esp32-c3]).
Build / upload / monitor speeds an order of magnitude faster than Arduino IDE.
CI-friendly — pio run, pio test, pio check work in headless GitHub Actions.

Single sketch (Arduino IDE) — MyProject.ino; fine for ≤200 lines.
PlatformIO project — src/, include/, lib/, test/, platformio.ini. The right default once you have multiple files or libs.
★ PlatformIO + git submodules / lib_deps from git — pin a library to a commit SHA for reproducible builds.
One platformio.ini env per board target — share src/ across an S3 build, a C3 build, and a release build with extra flags.
extra_scripts hooks — run pre/post-build Python (compress assets, generate version headers, update partition tables).

★ Arduino Library Manager (built into Arduino IDE / CLI) — curated registry; submit via PR to the Arduino library list.
★ PlatformIO Registry — superset of Arduino Library Manager + PlatformIO-native packages; resolves transitive deps.
Manual install — drop a folder into libraries/. Works, doesn't scale.
Git submodules — for things not in either registry, or when you want a specific commit.

Arduino is great for:

First-day learning, education, fast prototyping.
Glue-code projects with established libraries (sensors, displays, MQTT, OTA).
ESP32 work where the IDF-under-the-hood is exposed via #include <esp_*.h> from inside a sketch.

Arduino starts hurting when:

You need fine-grained RTOS scheduling (use ESP-IDF or Zephyr).
You're doing real DSP / fast IRQ work (drop to HAL/LL or use Embassy/Rust).
Your build needs hermeticity and CI determinism (Bazel / Nix / a real RTOS build system).
You're shipping millions of units and every byte of flash matters.

★ PlatformIO + GitHub Actions — pio run in CI; matrix-build across boards. The standard.
arduino/compile-sketches — official Arduino GH Action; compiles .ino sketches in CI.
Arduino lint (arduino-lint) — official linter for libraries / boards / cores; pairs with submitting to the Library Manager registry.
PlatformIO Check (pio check) — wraps Cppcheck / clang-tidy / PVS-Studio over your project.

First MCU project, no opinions yet: Arduino IDE 2.x.
Default for any non-trivial Arduino-style project: PlatformIO + VS Code.
CI / headless builds: Arduino-CLI or PlatformIO Core.
You're on an ESP32 and want IDF features mostly through Arduino: arduino-esp32 (it's IDF underneath).
You're on a Pi Pico: arduino-pico (Earle's core) for Arduino feel; or pivot to MicroPython / Pico-SDK.
You hate .ino files: PlatformIO with src/main.cpp.