emulator: Ardens
type: libretro
source: "https://github.com/tiberiusbrown/ardens"
profiled_date: "2026-03-18"
core_version: "Git"
display_name: "Arduboy (Ardens)"
cores:
  - ardens
systems:
  - arduboy

notes: |
  Ardens is an Arduboy FX simulator designed for profiling and debugging,
  ported to libretro. It emulates the ATmega32U4 MCU, SSD1306 OLED display,
  and W25Q128 external flash used by the Arduboy hardware.

  No BIOS or bootloader files are required. The core has all boot code
  compiled directly into the binary:

  - Caterina/Arduboy3K bootloaders for multiple hardware revisions (D1, D2,
    E2) are embedded as C arrays generated from .hex files via bin2c.py.
    Located in src/boot/boot_game_*.c and src/boot/boot_menu_*.c.
    The appropriate variant is selected at reset based on the configured
    device type (absim_arduboy.cpp:115-161).

  - Flashcart header (1536 bytes) is embedded in src/boot/boot_flashcart.c
    and written to the start of the W25Q128 flash image at init
    (absim_w25q128.hpp:14).

  - EEPROM (1024 bytes) and external flash (W25Q128, 16 MB) state are
    handled as save RAM through the libretro RETRO_MEMORY_SAVE_RAM
    interface, not as system files.

  The libretro port does not call RETRO_ENVIRONMENT_GET_SYSTEM_DIRECTORY
  and never attempts to load any file from the system directory.
  The .info file declares firmware_count = 0.

  Supported ROM formats: Intel HEX (.hex) and Arduboy package (.arduboy).
  block_extract is set to true (the core reads archives directly).

files: []

platform_details:
  embedded_bootloaders:
    source_ref: "src/boot/_make.bat, src/absim_arduboy.cpp:115-161"
    variants:
      - name: "arduboy3k-bootloader-game-sda"
        array: "ARDENS_BOOT_GAME_D1"
        size: 8422
        device: "Arduboy FX (SDA)"
      - name: "arduboy3k-bootloader-menu-sda"
        array: "ARDENS_BOOT_MENU_D1"
        size: 8422
        device: "Arduboy FX (SDA)"
      - name: "arduboy3k-bootloader-game-devkit"
        array: "ARDENS_BOOT_GAME_D2"
        size: 8446
        device: "Arduboy FX DevKit"
      - name: "arduboy3k-bootloader-menu-devkit"
        array: "ARDENS_BOOT_MENU_D2"
        size: 8446
        device: "Arduboy FX DevKit"
      - name: "arduboymini-bootloader-game"
        array: "ARDENS_BOOT_GAME_E2"
        size: 8548
        device: "Arduboy Mini"
      - name: "arduboymini-bootloader-menu"
        array: "ARDENS_BOOT_MENU_E2"
        size: 8548
        device: "Arduboy Mini"
    notes: |
      All bootloaders are compiled from Intel HEX into C arrays at build
      time. The core selects the game or menu variant at reset depending
      on whether a flashcart image was loaded and the boot_to_menu config
      flag (absim_arduboy.cpp:142-158). The bootloader is written to the
      top of the ATmega32U4 program memory at the address defined by the
      BOOTSZ fuse bits (absim.hpp:811).

  embedded_flashcart_header:
    source_ref: "src/boot/boot_flashcart.c, src/absim_w25q128.hpp:14"
    array: "ARDENS_BOOT_FLASHCART"
    size: 1536
    notes: |
      Empty flashcart header written to the first 1536 bytes of the
      W25Q128 flash image during initialization. This is not a BIOS
      file -- it is the default flash content the Arduboy FX expects
      at the start of external storage.