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# 1.3 USB Device HID Live Update

This example application shows how to use the Bootloader Library as a Live Update application using USB Device HID protocol on devices with Dual Bank Support.

Memory Layout

- For CORTEX-M based MCUs refer to the Live Update Memory Layout For CORTEX-M Based MCUs

- For MIPS Based MCUs refer to the Live Update Memory Layout For MIPS Based MCUs

Switcher Application (For PIC32MZ/PIC32MK Devices Only)

- This is a Switcher application which resides from the starting location of the Boot Flash memory region

  - A Custom linker file has to be added manually to project to place the application in Boot Flash Memory

- It Performs below operations

  - At reset it always maps the Program Flash Memory BANK 1 to lower memory region (0x9D000000)
  - At First Bootup it initializes the Flash Serial region of both banks and jumps to BANK 1 which is mapped to lower region (0x9D000000)
  - At subsequent resets it reads the Serial number from both the banks to decide which bank has the latest firmware

    - If Bank 1 serial number is greater than Bank 2 serial number it jumps to (0x9D000000) location, As Bank 1 is already mapped to lower region in above step application in Bank 1 starts running and this becomes Active Bank

    - If Bank 2 serial number is greater than Bank 1 serial number it maps Bank 2 to lower region by setting the Swap bit and jumps to (0x9D000000) location. As Bank 2 is mapped to lower region, application in Bank 2 starts running and this becomes Active Bank

Note: The Switcher project does not have any programing capabilities. It just performs above mentioned operation at reset.

Live Update Application

- This is a USB Device HID Live update application which resides from start of

  - Program Flash memory (0x9D000000) for PIC32MZ/PIC32MK Devices

    - A custom linker file live_update.ld will be generated by MCC to place the application in Program Flash memory

  - Internal Flash memory (0x00000000) for SAM Devices

- This project uses the USB Device HID Bootloader library to receive the new firmware to be programmed to Inactive Bank

  - Here the new firmware will be a updated version of same Live Update Application, As the firmware running in other bank needs to have the programming capability

- Apart from the programming capability this project can perform other application tasks simultanously which makes it a Live Update Application

- It calls the bootloader_Tasks() function which receives application to be programmed into Inactive Bank over the configured USB Device HID port

  - It uses the USB Device HID port with Product ID 0x3C to receive application hex from host PC using the Unified Bootloader Host Application

- It calls Application Tasks routine which

  - Blinks an LED every 1 second
  - Prints Messages over UART console

- It uses the On board Switch to

  - Update the Serial Number of Inactive bank where the new firmware is programmed and then trigger a reset to run new firmware for PIC32M devices

  - Swap the bank and trigger reset to run new firmware programmed in Inactive bank for SAM devices

Development Kits

The following table provides links to documentation on how to build and run USB Device HID Live Update on different development kits.