FastLED Platform: ARM SAMD21 (d21)

SAMD21 (Arduino Zero-class) support.

Files (quick pass)

• fastled_arm_d21.h: Aggregator for SAMD21; includes pin and clockless headers.
• fastpin_arm_d21.h: Pin helpers for direct GPIO access on SAMD21.
• led_sysdefs_arm_d21.h: SAMD21 system defines (interrupt policy, PROGMEM policy, etc.).
• clockless_arm_d21.h: Clockless WS281x driver built on arm/common/m0clockless.h (SysTick + inline ASM macros).

Notes:

• Clockless timing uses the M0/M0+ delay macros; ensure F_CPU and interrupt settings match board configuration.

Compile-time expectations

• FASTLED_USE_PROGMEM: 0 (per ARM SAMD guidance)
• FASTLED_ALLOW_INTERRUPTS: driver tolerates short windows; long ISRs may force a retry/punt

Optional feature defines

• FASTLED_USE_PROGMEM: Default 0.
• FASTLED_ALLOW_INTERRUPTS: Default 1. Enables FASTLED_ACCURATE_CLOCK when 1.

Define before including FastLED.h.