Embedded & Hardware

yosys4.8k★

Yosys turns hardware code into hardware. You describe a circuit in Verilog, and Yosys synthesizes it into the logic gates and flip-flops an FPGA or a chip is actually built from. It's the synthesis step in OpenROAD's open chip flow, and paired with nextpnr it programs Lattice iCE40, ECP5 and Gowin FPGAs with no vendor tools at all. It's free under the ISC license. The easy route is the free OSS CAD Suite, a nightly bundle with Yosys, nextpnr, the SBY formal checker and a VHDL plugin. Source builds need CMake 3.28 and GCC 13 or Clang 16. It's scriptable, so it fits CI. Releases ship monthly, and since 0.67 the free build reads a synthesizable subset of SystemVerilog through slang. YosysHQ sells Tabby CAD Suite, a commercial Yosys build with industrial SystemVerilog, VHDL and SVA (the assertion language verification teams write). Its calculator lists €500/month (about $562) for freelancers and €800/month (about $899) as the base for companies. Solo and small Verilog teams: free. VHDL or assertion-heavy teams: Tabby. The catch: inherited industrial code is exactly what's paid. Free VHDL only ships for Linux x64 and Apple Silicon, and Tabby licenses lock to one machine per 32 cores.

velxio3.5k★

Velxio emulates microcontroller boards in your browser, so you can write, compile and run Arduino, ESP32 or Raspberry Pi Pico code against real CPU emulation before you own a board. Wire sensors on a canvas, watch the Serial Monitor, debug without frying anything. The code is AGPLv3 and velxio.dev has a free plan. Self-hosting is one docker run of a prebuilt image, but that image covers only the Arduino, Pico and ESP32 families. STM32, Raspberry Pi Linux and partner boards like M5Stack stay on velxio.dev (licensed emulator binaries, big boot images). That's the open core line. Free hosted caps ESP32 runs at an hour, gives STM32 and Pi Linux three 15-minute trials each, and keeps projects public. Paid plans unlock those boards and the desktop app: No AI $4/month, Maker $7, Pro $19, cheaper yearly. Students and solo makers: free. Anyone on STM32 or Pi: No AI covers it. Pro if you want Claude Code driving the canvas. The catch: one maintainer writes nearly every commit, and the boards people pay for aren't in the open source image. Closed-source use needs a commercial license, price on request. Wokwi is the obvious hosted alternative; SimulIDE and Renode cover desktop.

Arduino_Core_STM323.4k★

This lets you program STM32 microcontrollers with the Arduino IDE instead of ST's heavier native toolchain. STM32 chips are the workhorses of embedded projects, drones, sensors, motor controllers, and their official tools have a real learning curve. This board-support core wraps them in the familiar Arduino API, so you write the usual setup and loop functions and it handles the rest. It's official, maintained by the stm32duino org, and free. Setup is about as easy as embedded gets. You paste a Boards Manager URL into the Arduino IDE, install the core, pick your board from a list of over a hundred, and flash over USB. Under the hood it's built on ST's official STM32Cube HAL and the GNU Arm toolchain, so you get real hardware support, not a toy abstraction. Newer versions need the Arduino IDE 2. If you're prototyping on a Nucleo or Discovery board, or moving an Arduino project onto more capable STM32 silicon, this is the fastest path. Hobbyists and makers get the most out of it. Serious firmware teams doing heavy debugging often still reach for PlatformIO or paid tools like Keil and IAR when they need deeper JTAG work, but for a huge range of projects the Arduino flow is plenty. The catch is the ceiling. The same Arduino abstraction that makes STM32 approachable also hides the low-level control that advanced embedded work eventually needs. You'll outgrow it on complex real-time or safety-critical projects. For everything up to that point, it's hard to beat free.

renode3.1k★

Renode does exactly that. Picture a virtual hardware lab where you run your actual firmware binary against simulated chips. built by Antmicro (embedded systems consultancy). Supports ARM Cortex-M/A, RISC-V, Xtensa, and other architectures. You define your hardware in a configuration file: CPU, memory, UART, SPI, I2C, GPIOs, and Renode simulates it cycle-accurately enough to run real firmware. Fully free to use. The license is listed as 'Other': it's the MIT license for most components. Antmicro provides commercial support, custom platform models, and integration services for enterprise customers, but the tool itself is free. Solo embedded developers: run firmware tests without buying dev boards. Small teams: CI/CD integration: test firmware on simulated hardware in your pipeline. Medium to large: simulate multi-device networks and test inter-device communication without a hardware lab. The catch: simulation is never perfect. Timing-sensitive firmware may behave differently on real hardware. Not every peripheral is modeled; you may need to write custom peripheral models for uncommon chips. And the documentation, while improving, assumes you already know embedded development. If you're not writing firmware, this tool has no use case for you.

sdk-nrf1.4k★

nRF Connect SDK is Nordic Semiconductor's official kit for writing firmware for its wireless chips, the nRF52, nRF53, nRF54, nRF70 and nRF91 families inside trackers, wearables, smart locks and cellular sensors. It sits on Zephyr, a tiny real-time operating system for microcontrollers, and adds Bluetooth LE, Thread, Matter, Wi-Fi, LTE-M/NB-IoT and DECT NR+ support plus a secure bootloader. It costs nothing. Setup is friendlier than most embedded toolchains. The nRF Connect for VS Code extension installs the SDK and a matching toolchain in one go; the command-line route uses nRF Util and SEGGER J-Link. Pin a stable release tag, don't track main. There's no paid SDK tier. Nordic makes its money on chips and sells nRF Cloud separately for device management and over-the-air updates. Solo and small teams: free, buy a dev kit. Larger teams shipping products: still free, but assign someone to track SDK upgrades and Nordic's security advisories. The catch: Nordic's own code isn't open source in the usual sense. Its license says it must only be used with a Nordic chip, and the binary libraries can't be reverse engineered. Want vendor freedom? Start from upstream Zephyr (Apache 2.0, still supports Nordic boards) or ESP-IDF on Espressif chips.

SnapmakerU1-Extended-Firmware1.1k★

SnapmakerU1-Extended-Firmware is a community firmware for the Snapmaker U1, a four-toolhead 3D printer, that opens up the stock system into a Klipper setup you actually control. You get a choice of Fluidd or Mainsail web dashboards, WebRTC camera streaming, a remote view of the touchscreen, Spoolman filament tracking with RFID tags, and SSH. It's free under GPLv3. Installing it works like a stock update: copy the .bin to a FAT32 USB stick and pick Local Update on the printer. Reverting is the same with Snapmaker's official file. Release images are built by GitHub Actions from Snapmaker's own firmware, checked against a pinned SHA-256, with checksums in every release. That's about as clean as custom firmware gets. Snapmaker gave it a first prize in its Innovation Fund this month. Solo makers to print farms: free. Optional add-ons like Tailscale and OctoEverywhere download on demand and carry their own pricing. The catch: installing it doesn't void the warranty, but Snapmaker won't cover damage it causes, and the Max Speed tweak pushes motion limits past stock. SSH ships with the root password snapmaker, so change it. And reproduce every bug on stock firmware before reporting it.