qmk_firmware/tmk_core/protocol/lufa/LUFA-120730/LUFA/DoxygenPages/SoftwareBootloaderJump.txt

/** \file
 *
 *  This file contains special DoxyGen information for the generation of the main page and other special
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 */

/**
 *  \page Page_SoftwareBootloaderStart Entering the Bootloader via Software
 *
 *  A common requirement of many applications is the ability to jump to the programmed bootloader of a chip
 *  on demand, via the code's firmware (i.e. not as a result of any physical user interaction with the
 *  hardware). This might be required because the device does not have any physical user input, or simply
 *  just to streamline the device upgrade process on the host PC.
 *
 *  The following C code snippets may be used to enter the bootloader upon request by the user application.
 *  By using the watchdog to physically reset the controller, it is ensured that all system hardware is
 *  completely reset to their defaults before the bootloader is run. This is important; since bootloaders
 *  are written to occupy a very limited space, they usually make assumptions about the register states based
 *  on the default values after a hard-reset of the chip.
 *
 *  \section Sec_SoftareBootAVR8 AVR8 Architecture
 *  The following software bootloader jump code is written for the AVR8 architecture.
 *
 *  \code
 *  #include <avr/wdt.h>
 *  #include <avr/io.h>
 *  #include <util/delay.h>
 *  
 *  #include <LUFA/Common/Common.h>
 *  #include <LUFA/Drivers/USB/USB.h>
 *  
 *  uint32_t Boot_Key ATTR_NO_INIT;
 *  
 *  #define MAGIC_BOOT_KEY            0xDC42ACCA
 *  #define BOOTLOADER_START_ADDRESS  (FLASH_SIZE_BYTES - BOOTLOADER_SEC_SIZE_BYTES)
 *  
 *  void Bootloader_Jump_Check(void) ATTR_INIT_SECTION(3);
 *  void Bootloader_Jump_Check(void)
 *  {
 *      // If the reset source was the bootloader and the key is correct, clear it and jump to the bootloader
 *      if ((MCUSR & (1 << WDRF)) && (Boot_Key == MAGIC_BOOT_KEY))
 *      {
 *          Boot_Key = 0;
 *          ((void (*)(void))BOOTLOADER_START_ADDRESS)();
 *      }
 *  }
 *  
 *  void Jump_To_Bootloader(void)
 *  {
 *      // If USB is used, detach from the bus and reset it
 *      USB_Disable();
 *      
 *      // Disable all interrupts
 *      cli();
 *      
 *      // Wait two seconds for the USB detachment to register on the host
 *      Delay_MS(2000);
 *      
 *      // Set the bootloader key to the magic value and force a reset
 *      Boot_Key = MAGIC_BOOT_KEY;
 *      wdt_enable(WDTO_250MS);
 *      for (;;);
 *  }
 *  \endcode
 *
 *  Note that the bootloader magic key can be any arbitrary value. The <em>FLASH_SIZE_BYTES</em> and
 *  <em>BOOTLOADER_SEC_SIZE_BYTES</em> tokens should be replaced with the total flash size of the AVR
 *  in bytes, and the allocated size of the bootloader section for the target AVR.
 *
 */