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69 lines
2.6 KiB
69 lines
2.6 KiB
/** \file
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*
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* This file contains special DoxyGen information for the generation of the main page and other special
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* documentation pages. It is not a project source file.
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*/
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/**
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* \page Page_SoftwareBootloaderStart Entering the Bootloader via Software
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*
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* A common requirement of many applications is the ability to jump to the programmed bootloader of a chip
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* on demand, via the code's firmware (i.e. not as a result of any physical user interaction with the
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* hardware). This might be required because the device does not have any physical user input, or simply
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* just to streamline the device upgrade process on the host PC.
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*
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* The following C code snippet may be used to enter the bootloader upon request by the user application.
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* By using the watchdog to physically reset the controller, it is ensured that all system hardware is
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* completely reset to their defaults before the bootloader is run. This is important; since bootloaders
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* are written to occupy a very limited space, they usually make assumptions about the register states based
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* on the default values after a hard-reset of the chip.
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*
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* \code
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* #include <avr/wdt.h>
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* #include <avr/io.h>
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* #include <util/delay.h>
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*
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* #include <LUFA/Common/Common.h>
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* #include <LUFA/Drivers/USB/USB.h>
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*
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* uint32_t Boot_Key ATTR_NO_INIT;
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*
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* #define MAGIC_BOOT_KEY 0xDC42ACCA
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* #define BOOTLOADER_START_ADDRESS (FLASH_SIZE_BYTES - BOOTLOADER_SEC_SIZE_BYTES)
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*
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* void Bootloader_Jump_Check(void) ATTR_INIT_SECTION(3);
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* void Bootloader_Jump_Check(void)
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* {
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* // If the reset source was the bootloader and the key is correct, clear it and jump to the bootloader
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* if ((MCUSR & (1<<WDRF)) && (Boot_Key == MAGIC_BOOT_KEY))
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* {
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* Boot_Key = 0;
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* ((void (*)(void))BOOTLOADER_START_ADDRESS)();
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* }
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* }
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*
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* void Jump_To_Bootloader(void)
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* {
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* // If USB is used, detatch from the bus
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* USB_ShutDown();
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*
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* // Disable all interrupts
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* cli();
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*
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* // Wait two seconds for the USB detachment to register on the host
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* for (uint8_t i = 0; i < 128; i++)
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* _delay_ms(16);
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*
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* // Set the bootloader key to the magic value and force a reset
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* Boot_Key = MAGIC_BOOT_KEY;
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* wdt_enable(WDTO_250MS);
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* for (;;);
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* }
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* \endcode
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*
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* Note that the bootloader magic key can be any arbitrary value. The <em>FLASH_SIZE_BYTES</em> and
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* <em>BOOTLOADER_SEC_SIZE_BYTES</em> tokens should be replaced with the total flash size of the AVR
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* in bytes, and the allocated size of the bootloader section for the target AVR.
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*
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*/
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