embedded systems

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MicroAlloc
2 months ago
- The author created a custom memory allocator (MicroAlloc) inspired by studying the esp-idf heap allocator.
- General-purpose heap allocators involve trade-offs between speed, overhead, and fragmentation.
- The implementation uses a first-fit free list allocator with a metadata structure that stores offsets instead of full pointers to minimize overhead (2 bytes per allocation).
- Embedded engineers should generally avoid dynamic allocation; static allocation, scratch buffers, block allocators, and arena allocators are safer alternatives.
- Free() implementation includes merging adjacent free blocks, but merging can be deferred via a compile-time flag for better performance.
The Rust on ESP Book
2 months ago
- This guide introduces embedded Rust development on Espressif products, covering the software stack, project generation, and tooling workflows.
- It targets Rust developers interested in embedded systems, even without prior experience, and suggests additional resources for background knowledge.
- Stable modules follow semantic versioning, but unstable components like esp-hal may change frequently and require careful dependency tracking.
- Additional resources include the Rust book, the Embedded Rust Book, no_std guides, and curated lists for Espressif and general embedded Rust.
- Contributions and bug reports are welcome via the book's repository, with community support available on Matrix and GitHub Discussions.
Linux on the Sega 32X. Who needs hardware synchronization primitives anyway?
3 months ago
- The author ports Linux to the Sega 32X as a way to improve board bringup skills, motivated by past experiences with Android 5.0 Lollipop on a MediaTek phone.
- The Sega 32X hardware features two SH2 CPUs and 256KB RAM, requiring creative solutions like using flash cart ROM as RAM and software synchronization for SMP support.
- Challenges include toolchain issues, memory constraints, lack of hardware synchronization primitives, and cache coherency, solved with Peterson's algorithm and 68000 as an interrupt router.
- The project successfully boots Linux with SMP support, a console display driver, and a minimal rootfs, despite performance limitations and extensive debugging.
An iroh powered smart fan
3 months ago
- The article demonstrates creating a smart fan using an ESP32 with Iroh, enabling remote temperature sensing and fan control without cloud components.
- It covers setting up the ESP32 with Iroh, adding a DHT22 sensor, implementing an IRPC protocol for remote communication, and developing a WebAssembly GUI for browser-based control.
- The project evolves from a simple echo server to a fully functional smart fan with authentication for setting temperature thresholds, and includes a 3D-printed enclosure for a finished product.
The Age of Personalized Hardware Is Coming
3 months ago
- Software is becoming increasingly personal, enabling individuals to build custom applications for work and life.
- Personal hardware devices are proliferating, with wearables alone exceeding 600 million units annually, driven by cheap components like ESP32 boards.
- The key issue is who writes the software for these devices, as current models restrict user control over device functionality.
- Agents require access to sensors (e.g., cameras, microphones) on devices to leverage physical context, necessitating software that runs locally.
- There is a growing demand for software tailored to many small, single-purpose devices for individual users.
- Platforms are opening up for software development, with tools like Pebble's open-source watch software, Meta/Mentra's web-based glasses development, and Google's WebXR making it accessible.
- The web serves as a trusted, proven foundation for building software, lowering barriers with coding agents aiding in setup and development.
- Current embedded toolchains (e.g., C++, SDKs) are complex and unlike web development, hindering broader interface creation for devices.
- GEA aims to raise the software boundary by allowing web-like development that compiles to native code for various platforms, without requiring embedded expertise.
- Hardware challenges (e.g., manufacturing, certification) remain, but the focus is on enabling more people to write software for personal devices.
- The future of personalized hardware hinges on software and who can write it, emphasizing user-driven development for tailored devices.
Lightning Memory-Mapped Database Manager (LMDB) 1.0
3 months ago
- LMDB is a Btree-based embedded database management library with a simplified BerkeleyDB-like API.
- It uses memory-mapped files for direct data access, eliminating the need for malloc or memcpy during fetches, resulting in high performance and simplicity.
- The database is fully transactional with ACID semantics, thread-aware, and supports concurrent read/write access across multiple processes and threads.
- Data pages employ copy-on-write, preventing overwrites and ensuring corruption resistance without special recovery after system crashes.
- Writes are serialized to avoid deadlocks, while readers operate without locks due to multi-versioning, allowing non-blocking read/write concurrency.
- Unlike write-ahead logs or append-only databases, LMDB requires no maintenance like checkpointing, as it reuses free pages to prevent unbounded file growth.
- Memory maps can be read-only (for corruption immunity) or read-write (for higher write performance, but with risk from buggy application code).
- Stale reader transactions or broken lockfiles can cause issues; fixes include using mdb_reader_check and handling semaphore ownership on BSD systems.

embedded systems

MicroAlloc

The Rust on ESP Book

Linux on the Sega 32X. Who needs hardware synchronization primitives anyway?

An iroh powered smart fan

The Age of Personalized Hardware Is Coming

Lightning Memory-Mapped Database Manager (LMDB) 1.0