/** \file * * This file contains special DoxyGen information for the generation of the main page and other special * documentation pages. It is not a project source file. */ /** * \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 snippet 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. * * \code * #include * #include * #include * * #include * #include * * 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 bootloader key is correct, clear it and jump to the bootloader * if (Boot_Key == MAGIC_BOOT_KEY) * { * Boot_Key = 0; * ((void (*)(void))BOOTLOADER_START_ADDRESS)(); * } * } * * void Jump_To_Bootloader(void) * { * // If USB is used, detatch from the bus and wait 2 seconds for the host to register it * USB_ShutDown(); * for (uint8_t i = 0; i < 128; i++) * _delay_ms(16); * * // 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 {FLASH_SIZE_BYTES} and * {BOOTLOADER_SEC_SIZE_BYTES} 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. * */