FastLED Platform: apollo3

Ambiq Apollo3 platform support.

Files (quick pass)

fastled_apollo3.h: Aggregator; includes fastpin_apollo3.h, fastspi_apollo3.h, clockless_apollo3.h.
fastpin_apollo3.h: Pin helpers using Ambiq fastgpio; board‑specific (pin,pad) mappings (e.g., SFE Edge/Thing Plus/ATP, Artemis Nano, LoRa Thing Plus expLoRaBLE). Defines HAS_HARDWARE_PIN_SUPPORT when applicable.
fastspi_apollo3.h: Bit‑banged SPI via fastgpio (all pins usable). Provides APOLLO3HardwareSPIOutput with writeBytes, writePixels, and bit‑level toggling.
clockless_apollo3.h: Clockless WS281x controller using SysTick for timing on Apollo3 Blue; sets FASTLED_HAS_CLOCKLESS.

Known‑good Arduino cores/boards:

SparkFun Apollo3 (Artemis) core and boards: Edge, Thing Plus, ATP, Artemis Nano, LoRa Thing Plus (expLoRaBLE)
Ambiq SDK‑based environments via the SparkFun core

Toolchain notes:

Uses Ambiq's fastgpio for high‑rate toggling where available; otherwise falls back to standard GPIO which is significantly slower.
Ensure your core exposes am_hal_gpio_* APIs used by fastpin_apollo3.h. When missing, hardware pin specialization will be disabled.

Timing caveats:

clockless_apollo3.h relies on SysTick for delay loops; large interrupt windows can corrupt WS281x signaling. Prefer short ISRs during frame output.
For best stability, keep Wi‑Fi/BLE stacks idle during show() and avoid heavy serial printing.