qmk_firmware/Bootloaders/MassStorage/BootloaderMassStorage.txt

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 *
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/** \mainpage Mass Storage Class USB AVR Bootloader
 *
 *  \section Sec_Compat Demo Compatibility:
 *
 *  The following list indicates what microcontrollers are compatible with this demo.
 *
 *  \li Series 7 USB AVRs (AT90USBxxx7)
 *  \li Series 6 USB AVRs (AT90USBxxx6)
 *  \li Series 4 USB AVRs (ATMEGAxxU4) - <i>See \ref SSec_Aux_Space</i>
 *  \li ATMEGA32U2 - <i>See \ref SSec_Aux_Space</i>
 *
 *  \section Sec_Info USB Information:
 *
 *  The following table gives a rundown of the USB utilization of this demo.
 *
 *  <table>
 *   <tr>
 *    <td><b>USB Mode:</b></td>
 *    <td>Device</td>
 *   </tr>
 *   <tr>
 *    <td><b>USB Class:</b></td>
 *    <td>Mass Storage Device</td>
 *   </tr>
 *   <tr>
 *    <td><b>USB Subclass:</b></td>
 *    <td>Bulk-Only Transport</td>
 *   </tr>
 *   <tr>
 *    <td><b>Relevant Standards:</b></td>
 *    <td>USBIF Mass Storage Standard \n
 *        USB Bulk-Only Transport Standard \n
 *        SCSI Primary Commands Specification \n
 *        SCSI Block Commands Specification</td>
 *   </tr>
 *   <tr>
 *    <td><b>Supported USB Speeds:</b></td>
 *    <td>Full Speed Mode</td>
 *   </tr>
 *  </table>
 *
 *  \section Sec_Description Project Description:
 *
 *  This bootloader enumerates to the host as a Mass Storage device, capable of reading and writing a new binary
 *  firmware image file, to load firmware onto the AVR.
 *
 *  Out of the box this bootloader builds for the AT90USB1287 with an 8KB bootloader section size, and will fit
 *  into 6KB of bootloader space. If you wish to alter this size and/or change the AVR model, you will need to
 *  edit the MCU, FLASH_SIZE_KB and BOOT_SECTION_SIZE_KB values in the accompanying makefile.
 *
 *  When the bootloader is running, the board's LED(s) will flash at regular intervals to distinguish the
 *  bootloader from the normal user application.
 *
 *  \warning <b>THIS BOOTLOADER IS NOT SECURE.</b> Malicious entities can recover written data, even if the device
 *           lockbits are set.
 *
 *  \section Sec_Installation Driver Installation
 *
 *  This bootloader uses the Mass Storage drivers inbuilt into all modern operating systems, thus no additional
 *  drivers need to be supplied for correct operation.
 *
 *  \section Sec_HostApp Host Controller Application
 *
 *  This bootloader is compatible with all operating systems that support the FAT12 file system format. To reprogram the
 *  device, overwrite a file stored on the virtual FAT filesystem with a new binary (BIN format) image. Remember to safely
 *  remove your device from the host using the host OS's ejection APIs, to ensure all data is correctly flushed to the
 *  bootloader's virtual filesystem and not cached in the OS's file system driver.
 *
 *  The current device firmware can be read from the device by reading a file from the virtual FAT filesystem.
 *
 *  \warning This bootloader is currently <b>incompatible with the Apple MacOS X OS Finder GUI</b>, due to the
 *           large amount of meta files this OS attempts to write to the disk along with the new binaries. On
 *           this platform, firmwares must be copied to the disk via the Terminal application only to prevent
 *           firmware corruption.
 *
 *  \section Sec_API User Application API
 *
 *  Several user application functions for FLASH and other special memory area manipulations are exposed by the bootloader,
 *  allowing the user application to call into the bootloader at runtime to read and write FLASH data.
 *
 *  By default, the bootloader API jump table is located 32 bytes from the end of the device's FLASH memory, and follows the
 *  following layout:
 *
 *  \code
 *  #define BOOTLOADER_API_TABLE_SIZE          32
 *  #define BOOTLOADER_API_TABLE_START         ((FLASHEND + 1UL) - BOOTLOADER_API_TABLE_SIZE)
 *  #define BOOTLOADER_API_CALL(Index)         (void*)((BOOTLOADER_API_TABLE_START + (Index * 2)) / 2)
 *
 *  void    (*BootloaderAPI_ErasePage)(uint32_t Address)               = BOOTLOADER_API_CALL(0);
 *  void    (*BootloaderAPI_WritePage)(uint32_t Address)               = BOOTLOADER_API_CALL(1);
 *  void    (*BootloaderAPI_FillWord)(uint32_t Address, uint16_t Word) = BOOTLOADER_API_CALL(2);
 *  uint8_t (*BootloaderAPI_ReadSignature)(uint16_t Address)           = BOOTLOADER_API_CALL(3);
 *  uint8_t (*BootloaderAPI_ReadFuse)(uint16_t Address)                = BOOTLOADER_API_CALL(4);
 *  uint8_t (*BootloaderAPI_ReadLock)(void)                            = BOOTLOADER_API_CALL(5);
 *  void    (*BootloaderAPI_WriteLock)(uint8_t LockBits)               = BOOTLOADER_API_CALL(6);
 *
 *  #define BOOTLOADER_MAGIC_SIGNATURE_START   (BOOTLOADER_API_TABLE_START + (BOOTLOADER_API_TABLE_SIZE - 2))
 *  #define BOOTLOADER_MAGIC_SIGNATURE         0xDCFB
 *
 *  #define BOOTLOADER_CLASS_SIGNATURE_START   (BOOTLOADER_API_TABLE_START + (BOOTLOADER_API_TABLE_SIZE - 4))
 *  #define BOOTLOADER_MASS_STORAGE_SIGNATURE  0xDF30
 *
 *  #define BOOTLOADER_ADDRESS_START           (BOOTLOADER_API_TABLE_START + (BOOTLOADER_API_TABLE_SIZE - 8))
 *  #define BOOTLOADER_ADDRESS_LENGTH          4
 *  \endcode
 *
 *  From the application the API support of the bootloader can be detected by reading the FLASH memory bytes located at address
 *  \c BOOTLOADER_MAGIC_SIGNATURE_START and comparing them to the value \c BOOTLOADER_MAGIC_SIGNATURE. The class of bootloader
 *  can be determined by reading the FLASH memory bytes located at address \c BOOTLOADER_CLASS_SIGNATURE_START and comparing them
 *  to the value \c BOOTLOADER_MASS_STORAGE_SIGNATURE. The start address of the bootloader can be retrieved by reading the bytes
 *  of FLASH memory starting from address \c BOOTLOADER_ADDRESS_START.
 *
 *  \subsection SSec_Aux_Space Auxiliary Bootloader Section
 *  To make the bootloader function on smaller devices (those with a physical bootloader section of smaller than 6KB) a second
 *  section of memory (called the <i>Auxiliary Bootloader Section</i>) is added before the start of the real bootloader section,
 *  and is filled with a portion of the bootloader code. This allows smaller devices to run the bootloader, at the cost of an
 *  additional portion of the device's FLASH (the bootloader section size in KB subtracted from the 6KB total size). A small
 *  trampoline is inserted at the start of the auxiliary section so that the bootloader will run normally in the case of a blank
 *  application section.
 *
 *  On devices supporting a 8KB bootloader section size, the AUX section is not created in the final binary.
 *
 *  \subsection SSec_API_MemLayout Device Memory Map
 *  The following illustration indicates the final memory map of the device when loaded with the bootloader.
 *
 *  \verbatim
 *  +----------------------------+ 0x0000
 *  |                            |
 *  |                            |
 *  |                            |
 *  |                            |
 *  |                            |
 *  |                            |
 *  |                            |
 *  |                            |
 *  |      User Application      |
 *  |                            |
 *  |                            |
 *  |                            |
 *  |                            |
 *  |                            |
 *  |                            |
 *  |                            |
 *  |                            |
 *  +----------------------------+ FLASHEND - BOOT_SECTION_SIZE - BOOT_AUX_SECTION_SIZE
 *  | Booloader Start Trampoline |
 *  | (Not User App. Accessible) |
 *  +----------------------------+ FLASHEND - BOOT_SECTION_SIZE - BOOT_AUX_SECTION_SIZE + 4
 *  |                            |
 *  |     Auxiliary Bootloader   |
 *  |  Space for Smaller Devices |
 *  | (Not User App. Accessible) |
 *  |                            |
 *  +----------------------------+ FLASHEND - BOOT_SECTION_SIZE
 *  |                            |
 *  |   Bootloader Application   |
 *  | (Not User App. Accessible) |
 *  |                            |
 *  +----------------------------+ FLASHEND - 96
 *  |   API Table Trampolines    |
 *  | (Not User App. Accessible) |
 *  +----------------------------+ FLASHEND - 32
 *  |    Bootloader API Table    |
 *  |   (User App. Accessible)   |
 *  +----------------------------+ FLASHEND - 8
 *  |   Bootloader ID Constants  |
 *  |   (User App. Accessible)   |
 *  +----------------------------+ FLASHEND
 *  \endverbatim
 *
 *  \section Sec_KnownIssues Known Issues:
 *
 *  \par In some cases, the application is not fully loaded into the device.
 *  Write-caching on some operating systems may interfere with the normal
 *  operation of the bootloader. Write caching should be disabled when using the
 *  Mass Storage bootloader, or the file system synced via an appropriate command
 *  (such as the OS's normal disk ejection command) before disconnecting the device.
 *
 *  \par After loading an application, it is not run automatically on startup.
 *  Some USB AVR boards ship with the BOOTRST fuse set, causing the bootloader
 *  to run automatically when the device is reset. In most cases, the BOOTRST
 *  fuse should be disabled and the HWBE fuse used instead to run the bootloader
 *  when needed.
 *
 *  \section Sec_Options Project Options
 *
 *  The following defines can be found in this demo, which can control the demo behaviour when defined, or changed in value.
 *
 *  <table>
 *   <tr>
 *    <th><b>Define Name:</b></th>
 *    <th><b>Location:</b></th>
 *    <th><b>Description:</b></th>
 *   </tr>
 *   <tr>
 *    <td>NO_APP_START_ON_EJECT</td>
 *    <td>AppConfig.h</td>
 *    <td>Define to disable automatic start of the loaded application when the virtual
 *        Mass Storage disk is ejected on the host.</td>
 *   </tr>
 *  </table>
 */