bia-microddr/bia_microddr_fw
1
0
Fork 0
Code Releases 1 Activity

added massive comment in memory.h about how memory is laid out to work with the bootloader. more code cleanup

Browse Source
This commit is contained in:
Boris Honman
2019-08-14 15:30:41 -04:00
parent 797f180a5c
commit 0d425faf6f
5 changed files with 99 additions and 25 deletions
Download Patch File Download Diff File Expand all files Collapse all files

93
common_src/memory.h
View File

@@ -28,21 +28,94 @@
#define MEMORY_
/**
* When changing the location of the application in flash memory these files and settings
* must be updated.
* In bootloader project:
* VectorRemap.asm HiVector goto -> APP_FW_MEMORY_OFFSET + 0x08
* LoVector goto -> APP_FW_MEMORY_OFFSET + 0x18
* Configuration > Linker > Memory Model > ROM space -> default,-APP_FW_MEMORY_OFFSET-7FFF
* In application project:
* Configuration > Linker > Memory Model > ROM space -> default,-0-[[APP_FW_MEMORY_OFFSET-1]],-[[APP_FW_MEMORY_OFFSET+6]]-[[APP_FW_MEMORY_OFFSET+7]],-[[APP_FW_MEMORY_OFFSET+0x16]]-[[APP_FW_MEMORY_OFFSET+0x17]]
* ##########################################################################################
* ### Regarding the modified memory layout of program flash to accomodate the bootloader ###
* ##########################################################################################
*
* This firmware implements a bootloader to allow the user to flash firmware over USB without requiring an external
* programmer/debugger such as the ICD or Pickit 3. The bootloader and the application are separate binaries that
* are compiled and linked independently of each other.
*
* The bootloader occupies memory in program flash starting at address 0x0000. The MCU will always start program
* execution at this address. The application occupies program flash memory starting from a predetermined address after
* the end of the memory space occupied by the bootloader through the remainder of the program flash memory. As an
* example let's assume the application starts at address 0x1400. The memory map of the corresponding program flash is
* shown below.
*
* ###############################
* # Memory Map of Program Flash #
* ###############################
*
* Address Description
* ------------------------
* 0x0000 Bootloader reset vector
* 0x0008 Bootloader interrupt vector (high)
* 0x0018 Bootloader interrupt vector (low)
* ...
* 0x0030 Bootloader absolute entrypoint (application can enter bootloader by jumping to this address)
* ==[Remainder of bootloader code]==
* 0x1400 Application reset vector
* 0x1406 Application signature word**
* 0x1408 Application interrupt vector (high)****
* 0x1416 Application version word***
* 0x1418 Application interrupt vector (low)****
* ==[Remainder of application code]==
* 0x7FFF (Last byte of program flash)
*
* Notes: ** The signature word is written with a known value by the bootloader after it writes the application
* code to flash memory and verifies the data written. If the bootloader does not read this exact value
* at this address at startup it will assume the application code is corrupted and immediately enter
* firmware update mode so valid application code can be flashed.
* *** The version word is stored at this address by the application code at link time. Currently unused
* but I'm leaving the functionality in so the bootloader can report the version of the current
* application.
* **** The bootloader's interrupt vectors will forward interrupts to the application's interrupt vectors
* because they were moved when we offset the application code to 0x1400.
*
* ##############################################
* # Changing the application's memory location #
* ##############################################
*
* 2 source files must be modified, as well as the project configurations for both the bootloader and application
* projects.
*
* #
* # File changes
* #
* File Location Changes
* ------------------------------------------------
* VectorRemap.asm bootloader * Change address in HiVector goto instruction to address of application
* high priority interrupt vector (ex. 0x1408).
* * Change address in LoVector goto instruction (NOT the goto 0x30) to address
* of application low priority interrupt vector (ex. 0x1418).
* THIS FILE shared * Change APP_FW_MEMORY_OFFSET to the starting address of the application
* (ex. 0x1400)
*
* #
* # BOOTLOADER project configuration changes
* #
* Configuration > Linker > Memory Model > ROM space
* * Add memory range of application as a protected region. Ranges are separated by a single comma. Ranges that
* start with a '-' will be considered protected. Memory addresses specified in hexadecimal. No spaces allowed.
* (ex. 'default,-1400-7FFF')
*
* #
* # APPLICATION project configuration changes
* #
* Configuration > Linker > Memory Model > Additional Options > Code offset
* * Set to APP_FW_MEMORY_OFFSET
* Configuration > Linker > Memory Model > ROM space
* * Add memory ranges for bootloader, application signature word, and application version word as protected
* regions. Ranges are separated by a single comma. Ranges that start with a '-' will be considered protected.
* Memory addresses specified in hexadecimal. No spaces allowed.
* (ex. 'default,-0-13FF,-1406-1407,-1416-1417')
*/
/**
* The base address of the application memory space. The application's reset vector will be
* at this address.
*/
#define APP_FW_MEMORY_OFFSET 0x2000
#define APP_FW_MEMORY_OFFSET 0x1400
/**
* The address in application memory space that stores the application's version number.
@@ -59,7 +132,7 @@
* The absolute address of the bootloader entrypoint. The application can jump to the
* bootloader by executing a "goto" instruction with this address.
*/
#define BOOTLOADER_ENTRYPOINT 0x001C
#define BOOTLOADER_ENTRYPOINT 0x0030
#endif /* MEMORY_ */