SoftwareBootloaderJump.txt 2.51 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
/** \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 <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})
 *  
34
35
 *  void Bootloader_Jump_Check(void) ATTR_INIT_SECTION(3);
 *  void Bootloader_Jump_Check(void)
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
 *  {
 *      // 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.
 * 
 */