grblHAL/core is a production-grade, real-time CNC motion control firmware derived from the classic Grbl project. It implements a full RS274/NGC G‑code interpreter, acceleration‑planned trajectory generator, and stepper motor execution capable of driving 3–8 axes with kinematics support (Cartesian, CoreXY, delta, polar, and 5‑axis RTCP). The codebase is structured as a hardware‑agnostic core with a Hardware Abstraction Layer (HAL), allowing easy porting to 32‑bit MCUs (STM32, ESP32, RP2040, etc.). It includes modular subsystems for spindle control (PWM, VFD, stepper, encoder‑sync), coolant, probing, tool change, limits/homing, soft limits, backlash compensation, threading (G76), and laser/plasma modes. Communication is handled via multiple streams (serial, Telnet, WebSocket, Bluetooth) and protocols (Modbus RTU/TCP, CAN bus). A lightweight virtual file system (VFS) with mountable storage (RAM, embedded, SD, LittleFS) is provided, along with a plugin system for optional features like WebUI, Trinamic drivers, and encoders. The architecture is driven by event hooks (`grbl.on_*` callbacks) and function pointers in `hal`, enabling driver and plugin customization without modifying core code. The settings system (`settings.c/h`) allows runtime configuration persistence with type‑safe registration, validation, and iteration. Real‑time operation is achieved with a foregound/background task model, ISR‑safe data structures (lock‑free override rings), and a planner ring buffer with lookahead and jerk‑controlled acceleration profiles. The code is extensively tested via an external unit test suite and includes compatibility levels for legacy Grbl behavior. This repository is solely an application (embedded firmware). It does not contain data pipelines, notebooks, or research analysis. The code is heavily optimized for resource‑constrained MCUs, with generous use of conditional compilation (`#ifdef` blocks) to select features, drivers, and platform specifics. While the resulting complexity can increase maintenance overhead, the modular design and active maintenance (last commit 2026‑10‑15, ongoing issue triage) indicate a well‑sustained project. Key reusable patterns include the HAL abstraction, the settings registration framework, the stream management layer, and the VFS mount system — all of which can be extracted for other embedded projects with minimal adaptation.