AN1388 â PIC32 Bootloader - Microchip

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AN1388PROGRAM FLASHThe PC host application sends one or multiple hexrecords in Intel Hex format along with the programFlash command. The MPLAB C32 compiler generatesthe image in the Intel Hex format. Each line in the Intelhexadecimal file represents a hexadecimal record.Each hexadecimal record starts with a colon (:) and isin ASCII format. The PC host application discards thecolon and converts the remaining data from ASCII tohexadecimal, and then sends the data to thebootloader. The bootloader extracts the destinationaddress and data from the hex record, and writes thedata into program Flash.The request frame from the PC host application to thebootloader is shown in Example 6.JUMP TO APPLICATIONThe Jump to Application command from the PChost application commands the bootloader to executethe application. The request frame from the PC hostapplication to the bootloader is shown in Example 10.EXAMPLE 10: REQUEST[…]There is no response to this command from thebootloader because the bootloader immediately exitsthe firmware upgrade mode and begins executing theapplication.EXAMPLE 6: REQUEST[…][…]Where:HEX_RECORD is the Intel Hex record in hexadecimal formatThe response from the bootloader to the PC hostapplication is shown in Example 7.EXAMPLE 7:RESPONSE[…]READ CRCThe read CRC command is used to verify the contentof the program Flash after programming. The requestframe from the PC host application to the bootloader isshown in Example 8.EXAMPLE 8:REQUEST[…]ADRS_LB, ADRS_HB, ADRS_UB and ADRS_MB, asshown in Example 8, represent the 32-bit Flashaddresses from where the CRC calculation begins.NUMBYTES_LB, NUMBYTES_HB, NUMBYTES_UB andNUMBYTES_MB, as shown in Example 8, represent thetotal number of bytes in 32-bit format for which the CRCis to be calculated.The response from the bootloader to the PC hostapplication is shown in Example 9.EXAMPLE 9: RESPONSE[…]DS01388B-page 10© 2011-2012 Microchip Technology Inc.
AN1388APPENDIX C:CONSIDERATIONSWHILE MOVING THEAPPLICATION IMAGEThis section describes the procedure to place a userapplication into a desired program Flash memoryregion. It must be ensured that the user application’smemory region does not overlap with the memoryregion reserved for the bootloader.1. Create a new text file and save it with a .ld fileextension.2. Add the new *.ld file to your project. The new*.ld file appears in the project tree.3. Starting with the default linker script is easierthan starting from the scratch. Use a text editorto copy the contents of the \pic32mx\lib\ldscripts\elf32pic32mx.x default linkerscript into the newly created *.ld file. TheINCLUDE procdefs.ld directive should bereplaced with the contents of device specific \pic32mx\lib\proc\device\procdefs.ldportion of the linker script. The path \pic32mx\lib is located inside the folder where C32compiler tools are installed.4. Edit the newly created *.ld file to remap thelinker script memory regions exception_mem,kseg0_boot_mem, kseg1_boot_mem andkseg0_program_mem into the program Flashreserved for the user application. Theexception_mem must align on a 4K addressboundary of the program Flash as shown inExample 11.For more information on linker script memoryregions, refer to the “MPLAB ® Assembler, Linkerand Utilities for PIC32 MCUs User’s Guide”(DS51833) and the “MPLAB ® C Compiler forPIC32 MCUs User’s Guide” (DS51686).5. Set the value of _ebase_address to theORIGIN value of exception_mem.6. Change the values of memory addresses_RESET_ADDR, _BEV_EXCPT_ADDR and_DBG_EXCPT_ADDR, so that all theseaddresses fall inside kseg1_boot_mem.7. Clean and build the application project to get aremapped application image.Note: The modified application linker script file isnot suitable for building the application indebug or stand-alone (to use withoutbootloader) mode.The next step following the application remap isinforming the bootloader about the new location andreset address of the user application in the programFlash.The bootloader code provides compile time options forthis purpose. The macros,APP_FLASH_BASE_ADDRESSandAPP_FLASH_END_ADDRESS, define the start and theend addresses of the program Flash reserved for theuser application. The bootloader performs an erase orprogram operation only if the target address of theFlash is within these addresses. Therefore, the usermust set new start and end address values to thesemacros following the application remap. Set theaddresses so that exception_mem,kseg0_boot_mem, kseg1_boot_mem, andkseg0_program_mem defined in the procdefs.ldfile of the user application are within these addresses,as shown in Example 12.The macro, USER_APP_RESET_ADDRESS, specifiesthe reset address of the user application. Thebootloader branches to this address when it must runthe user application. The value of this macro must bechanged to _RESET_ADDR defined in theprocdefs.ld file of the user application project. Thebootloader project must be recompiled andprogrammed into the PIC32 device after modifyingthese macros.© 2011-2012 Microchip Technology Inc. DS01388B-page 11
Page 1 and 2: AN1388PIC32 BootloaderAuthor:INTROD
Page 3 and 4: AN1388IMPLEMENTATION OVERVIEW(UART,
Page 5 and 6: AN1388HANDLING DEVICE CONFIGURATION
Page 7 and 8: AN1388RUNNING THE SD CARDBOOTLOADER
Page 9: AN1388APPENDIX B:BOOTLOADERCOMMUNIC
Page 13 and 14: AN1388EXAMPLE 12:LINES TO MODIFY IN
Page 15 and 16: AN1388APPENDIX E:BOOTLOADERWORKSPAC
Page 17 and 18: AN1388APPENDIX F:REVISION HISTORYRe
Page 19 and 20: Note the following details of the c

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AN1388 â PIC32 Bootloader - Microchip