1.8.3 USB Host MSD Bootloader Configurations

Bootloader Specific User Configurations

• Bootloader Media Type:

  • Change the Media Type to USB Mass Storage Device

• Bootloader NVM Memory Used:

  • Specifies the memory peripheral used by bootloader to perform Flash operations
  • The name of the peripheral will vary from device to device

• Bootloader Size (Bytes):

  • Specifies the maximum size of Flash required by the bootloader
  • This size is calculated based on Bootloader type and Memory used
  • This size will vary from device to device and should always be aligned to device erase unit size

• Enable Bootloader Trigger From Firmware:

  • This Option can be used to Force Trigger bootloader from application firmware after a soft reset. It does so by reserving the specified number of bytes in SRAM from the start of the RAM. The reserved memory is updated by the application with a pre-defined pattern. The bootloader firmware in the bootloader_Trigger() routine, can check the reserved memory for the pre-defined pattern and enter Bootloader mode if the pattern matches.

  • Number Of Bytes To Reserve From Start Of RAM:

    • This option adds the provided offset to RAM Start address in bootloader linker script
    • Application firmware can store some pattern in the reserved bytes region from RAM start for bootloader to check at reset in bootloader_Trigger() function

• Application Binary Image Path:

  • Application binary image file name with path. If only file name is mentioned bootloader will try to open the file from the root directory

  • Default: image.bin

  • Can be used to specify custom paths based on requirement

    • Example: dir1/dir2/app.bin

File System Configurations

• Use File System Auto Mount Feature:

  • Enabled by default when File System Bootloader is added

• Media Type:

  • Change the Media Type to SYS_FS_MEDIA_TYPE_MSD

• Make FAT File System Read-only:

  • Enabled by default when File System Bootloader is added as there are no write operations to be done

  • Enabling this option also saves significant amount of Flash memory

Bootloader System Configurations

• Application Start Address (Hex):
  • Start address of the application which will programmed by bootloader
  • This value is filled by bootloader when its loaded which is equal to the bootloader size. It can be modified as per user need.
  • This value will be used by bootloader to jump to application at device reset

Bootloader Linker Pre Processor Macros for Cortex-M Based MCUs

• Based on the configurations the above linker pre processor macros will be generated in MPLAB X xc32-ld settings
  • ROM_LENGTH specifies the size of the bootloader