FastLED Platform: arm

ARM support for a wide range of MCUs (Teensy 3.x/4.x, SAMD21/SAMD51, RP2040, STM32, Renesas UNO R4, nRF5x, etc.).

Top-level files (quick pass)

• arm_compile.hpp: Hierarchical include hook for ARM (e.g., Teensy 4.x __IMXRT1062__). Source inclusion is handled by CMake globs.
• compile_test.hpp: Compile-time assertions for platform flags on ARM families (PROGMEM usage, interrupts policy, F_CPU, memory hints).
• int.h: ARM-friendly integer and pointer typedefs in fl::.

Subplatform directories

• common/: Shared helpers for Cortex-M0/M0+; m0clockless.h provides SysTick fallback and clockless ASM macros used by SAMD21, etc.
• d21/: SAMD21 family (e.g., Arduino Zero-class). Includes clockless_arm_d21.h and pin helpers.
• d51/: SAMD51 family (e.g., Feather M4, ItsyBitsy M4, Wio Terminal). Clockless + SPI core integration.
• giga/: Arduino GIGA R1 (STM32H747). LED sysdefs and clockless/SPI wiring for this target.
• k20/: Teensy 3.x (MK20DX). Clockless + block clockless, fastspi_arm_k20.h, and integrations: octows2811_controller.h, ws2812serial_controller.h, smartmatrix_t3.h.
• k66/: Teensy 3.6 (K66). Similar to k20 with clockless and block variants; reuses some k20 controllers.
• kl26/: Teensy LC (KL26Z64). Clockless and ws2812serial_controller support.
• mxrt1062/: Teensy 4.x (i.MX RT1062). Clockless and block clockless, plus OctoWS2811 and SmartMatrix integrations.
• nrf51/: Nordic nRF51. Clockless and pin/SPI wiring for this series.
• nrf52/: Nordic nRF52. Adds arbiter_nrf52.h (PWM resource arbitration), clockless, pin/SPI, and sysdefs.
• renesas/: Renesas RA4M1 (Arduino UNO R4). Clockless + SPI core integration and sysdefs.
• rp2040/: Raspberry Pi Pico (RP2040). Clockless via PIO; pio_gen.h builds a PIO program from T1/T2/T3 at runtime.
• sam/: Arduino Due (SAM3X). Clockless and block clockless, pin/SPI wiring for SAM.
• stm32/: STM32 (e.g., F1). Pin helpers and clockless driver for STM32 family.

Quick guidance per subplatform

• d21 (SAMD21): FASTLED_USE_PROGMEM=0; clockless via arm/common/m0clockless.h. Keep ISRs short; SysTick‑based timing.
• d51 (SAMD51): Higher clocks; enable interrupts cautiously. Prefer minimal critical sections.
• k20/k66 (Teensy 3.x): DWT cycle counter timing; long ISRs can force retries. OctoWS2811/SmartMatrix available.
• mxrt1062 (Teensy 4.x): Very high frequency; mind DWT and interrupt thresholds. Parallel output offload recommended for large installations.
• rp2040: PIO‑driven; ensure T1/T2/T3 match LED timing; regenerate PIO program when timings change.
• nrf51/nrf52: Budget interrupt windows conservatively. On nrf52, arbitrate PWM instances via arbiter_nrf52.h.
• renesas (UNO R4): Ensure sysdefs set FASTLED_USE_PROGMEM=0; verify cli/sei equivalents and F_CPU.
• stm32/giga: Use ARM IRQ wrappers in sysdefs; direct register access varies by core.