grblHAL/core is an embedded firmware for real-time CNC motion control, derived from the original grbl 1.1f project. It interprets G-code (RS274/NGC) and executes motion planning with acceleration/jerk profiles, driving stepper motors via a hardware abstraction layer (HAL) that supports many 32-bit MCUs (ESP32, STM32, RP2040, i.MX RT, etc.). The architecture is modular: a plugin system allows adding spindles, I/O expanders, kinematics (CoreXY, delta, polar, wall plotter), networking, and custom M-codes. Key subsystems include a G-code parser, motion planner with look-ahead, stepper ISR with Bresenham and AMASS, state machine, settings registry with NVS persistence, virtual file system, and cooperative task scheduler. Communication streams (serial, TCP, WebSocket, Modbus) are multiplexed. The codebase is highly optimized for real-time constraints, uses extensive conditional compilation for configurability, and provides reusable patterns such as function-pointer-based HAL, callback chaining, and abstracted I/O. While some internal coupling exists, many modules (crc, regex, utf8, string utilities, PID, expression evaluator, task scheduler) are self-contained and extractable.