LUFA/DoxygenPages/SoftwareBootloaderJump.txt

   1 /** \file
   2  *
   3  *  This file contains special DoxyGen information for the generation of the main page and other special
   4  *  documentation pages. It is not a project source file.
   5  */
   6
   7 /**
   8  *  \page Page_SoftwareBootloaderStart Entering the Bootloader via Software
   9  *
  10  *  A common requirement of many applications is the ability to jump to the programmed bootloader of a chip
  11  *  on demand, via the code's firmware (i.e. not as a result of any physical user interaction with the
  12  *  hardware). This might be required because the device does not have any physical user input, or simply
  13  *  just to streamline the device upgrade process on the host PC.
  14  *
  15  *  The following C code snippets may be used to enter the bootloader upon request by the user application.
  16  *  By using the watchdog to physically reset the controller, it is ensured that all system hardware is
  17  *  completely reset to their defaults before the bootloader is run. This is important; since bootloaders
  18  *  are written to occupy a very limited space, they usually make assumptions about the register states based
  19  *  on the default values after a hard-reset of the chip.
  20  *
  21  *  \section Sec_SoftareBootAVR8 AVR8 Architecture
  22  *  The following software bootloader jump code is written for the AVR8 architecture.
  23  *
  24  *  \code
  25  *  #include <avr/wdt.h>
  26  *  #include <avr/io.h>
  27  *  #include <util/delay.h>
  28  *
  29  *  #include <LUFA/Common/Common.h>
  30  *  #include <LUFA/Drivers/USB/USB.h>
  31  *
  32  *  uint32_t Boot_Key ATTR_NO_INIT;
  33  *
  34  *  #define MAGIC_BOOT_KEY            0xBADCAFE5
  35  *  #define BOOTLOADER_START_ADDRESS  ((FLASH_SIZE_BYTES - BOOTLOADER_SEC_SIZE_BYTES) >> 1)
  36  *
  37  *  void Bootloader_Jump_Check(void) ATTR_INIT_SECTION(3);
  38  *  void Bootloader_Jump_Check(void)
  39  *  {
  40  *      // If the reset source was the bootloader and the key is correct, clear it and jump to the bootloader
  41  *      if ((MCUSR & (1 << WDRF)) && (Boot_Key == MAGIC_BOOT_KEY))
  42  *      {
  43  *          Boot_Key = 0;
  44  *          ((void (*)(void))BOOTLOADER_START_ADDRESS)();
  45  *      }
  46  *  }
  47  *
  48  *  void Jump_To_Bootloader(void)
  49  *  {
  50  *      // If USB is used, detach from the bus and reset it
  51  *      USB_Disable();
  52  *
  53  *      // Disable all interrupts
  54  *      cli();
  55  *
  56  *      // Wait two seconds for the USB detachment to register on the host
  57  *      Delay_MS(2000);
  58  *
  59  *      // Set the bootloader key to the magic value and force a reset
  60  *      Boot_Key = MAGIC_BOOT_KEY;
  61  *      wdt_enable(WDTO_250MS);
  62  *      for (;;);
  63  *  }
  64  *  \endcode
  65  *
  66  *  Note that the bootloader magic key can be any arbitrary value. The <em>FLASH_SIZE_BYTES</em> and
  67  *  <em>BOOTLOADER_SEC_SIZE_BYTES</em> tokens should be replaced with the total flash size of the AVR
  68  *  in bytes, and the allocated size of the bootloader section for the target AVR.
  69  *
  70  */
  71