wrobot/v1.2/Shibo-main-TOMMY/lib/FastLED/src/platforms/avr/README.md

FastLED Platform: avr

AVR support for classic Arduino boards (e.g., ATmega328P/UNO) and many ATtiny/ATmega variants.

What’s here (quick pass)

• avr_compile.hpp: Hierarchical include; ties AVR sources together when FASTLED_ALL_SRC is enabled (CMake globs bring .cpp in).
• avr_millis_timer_null_counter.hpp: Defines a weak (or strong on some ATtiny) volatile unsigned long timer_millis symbol for boards missing a timer implementation.
• avr_millis_timer0_impl_source.hpp: Minimal Timer0/TCA0 ISR-based timer_millis implementation for select ATtinyx/y parts; initialized via constructor.
• avr_millis_timer_source.cpp: Chooses between weak symbol vs. implementation based on macros/board, includes the two headers above.
• avr_pin.h: Core _AVRPIN template used by FastPin<> specializations for direct port IO (hi/lo/toggle, masks, ports).
• clockless_trinket.h: AVR clockless LED controller with tight-timing bit-banging (WS2811/WS2812). Docs on interrupt impact and timing macros.
• compile_test.hpp: Compile-time checks for AVR config (e.g., FASTLED_USE_PROGMEM==1, FASTLED_ALLOW_INTERRUPTS==0, F_CPU sanity).
• fastled_avr.h: Aggregator header enabling PROGMEM and including fastpin_avr.h, fastspi_avr.h, clockless_trinket.h.
• fastpin_avr.h: Dispatcher that includes either fastpin_avr_nano_every.h or fastpin_avr_legacy.h (ATmega4809/Nano Every vs. other AVRs).
• fastpin_avr_atmega4809.h: Pin mappings using VPORT for ATmega4809 parts; defines AVR_HARDWARE_SPI, HAS_HARDWARE_PIN_SUPPORT, SPI pin IDs.
• fastpin_avr_nano_every.h: Pin mappings using VPORT for Arduino Nano Every (ATmega4809 variant); hardware SPI constants.
• fastpin_avr_legacy.h: Large legacy “god-header” of pin mappings for many ATtiny/ATmega families; sets HAS_HARDWARE_PIN_SUPPORT and SPI aliases where applicable.
• fastspi_avr.h: SPI backends for AVR: UART MSPI (USART0/1) and hardware SPI (SPI/SPDR, SPI0) variants; writeBytes/writePixels helpers.
• int.h: AVR-friendly integer typedefs in fl:: (e.g., i16, u16, i32, u32) and pointer/size aliases.
• io_avr_lowlevel.h: Low-level UART register helpers (UDR/UCSR mapping) plus avr_uart_putchar/available/read utilities.
• io_avr.h: Simple print/println and input helpers that use low-level UART if available, else fallback to Arduino Serial.
• led_sysdefs_avr.h: AVR platform defines (FASTLED_AVR), interrupt policy defaults, PROGMEM default, MS_COUNTER binding for millis symbols, small-device flags.

Millis provider selection

• Boards with a working Arduino core millis() typically use the weak timer_millis symbol from avr_millis_timer_null_counter.hpp (no extra ISR).
• Select ATtiny parts (e.g., some x/y families) use avr_millis_timer0_impl_source.hpp to provide a minimal Timer0/TCA0 ISR that increments timer_millis.
• avr_millis_timer_source.cpp chooses between the two at compile time based on board macros.

Supported families (summary)

Covered in fastpin_avr_legacy.h and fastpin_avr_atmega4809.h:

• ATmega328P/32U4/1280/2560 series
• ATmega4809 (Arduino Nano Every) via VPORT mappings
• ATtiny85/84/861 and newer tinyAVR 0/1‑series variants (where supported)

Quirks:

• Strict ISR timing: for WS281x, set FASTLED_ALLOW_INTERRUPTS=0 on small AVRs for best signal integrity.
• SPI routes differ (SPI vs SPI0, UART MSPI). The SPI backend handles these variants; verify MOSI/SCK pins per board.

Optional feature defines

• FASTLED_USE_PROGMEM: Default 1 on AVR. Required for flash‑resident tables.
• FASTLED_ALLOW_INTERRUPTS: Default 0 on AVR. You may set to 1 on faster parts but expect tighter timing constraints.
• FASTLED_FORCE_SOFTWARE_SPI: Force software (bit‑bang) SPI even when hardware SPI is available (commented hint in fastspi_avr.h).
• FASTLED_DEFINE_AVR_MILLIS_TIMER0_IMPL: Force Timer0 millis provider implementation for boards lacking Arduino millis().
• FASTLED_DEFINE_TIMER_WEAK_SYMBOL: Control weak symbol export for timer_millis in avr_millis_timer_source.cpp.

Define these before including FastLED.h.