This project enhances the STM32WB55 BLE OTA example by providing A/B slots for firmware updates. Unlike the original example, which only updates one firmware, this project allows for up to two images to be stored in separate slots. This approach reduces the risk of bricking devices during an update, as users can revert to the previous version if necessary.

• OTA Application Start Address: 0x08000000
• A Slot Address: 0x08008000 - 0x08047fff
• B Slot Address: 0x08048000 - 0x08087fff
• Context Size for Each Slot: 0x040000 (256 kB)

The following changes have been made to enable A/B system updates:

• Defined start sector indices for A and B slots to CFG_APP_SLOT_A_START_SECTOR_INDEX and CFG_APP_SLOT_B_START_SECTOR_INDEX, respectively.

• Added structures to manage A/B bootloader control.
• Implemented functions to select the boot slot, print slot status, and prompt user for boot selection.

• Added a script to configure linker settings for flashing images into A/B slots.

• STM32CubeIDE
• STM32CubeProgrammer
• STM32WB55 Nucleo Board
• Android/iOS device with the ST BLE Sensor application

1. Program Image/BLE_ota.bin to your board at address 0x08000000 using STM32CubeProgrammer.
2. Download Image/BLE_HeartRate_ota_A.bin and Image/BLE_HeartRate_ota_B.bin to your phone.
3. Power up the board.
4. Connect to the STM_OTA device using the ST BLE Sensor application.
5. Choose firmware upgrade and customize update parameters as follows:
   • For A Slot:
     • First sector to delete: 8
     • Number of sectors to delete: 40
     • Select firmware: BLE_HeartRate_ota_A.bin
   • For B Slot:
     • First sector to delete: 72
     • Number of sectors to delete: 40
     • Select firmware: BLE_HeartRate_ota_B.bin
6. After the update, the bootloader will wait for you to select the system image to boot. The console log will display the status of both slots.

   Welcome to A/B system bootloader!
   Slot A: O
   Slot B: X
   
   Slot A(a), Slot B(b), BLE OTA(c)
   Select an app to start on: 
   

1. Download the STM32Cube MCU Package from here.
2. Clone this project into STM32Cube_FW_WB_V1.18.0/Projects/P-NUCLEO-WB55.Nucleo/Applications/BLE/.
3. Import the project into STM32CubeIDE for building the image.

1. Create a new BLE HeartRate OTA example in STM32CubeIDE.
2. Copy script/config_linker.sh into the workspace.
3. Modify the linker script path in it for your case:

   LINKER_SCRIPT="BLE_HeartRate_ota/STM32CubeIDE/STM32WB55RGVX_FLASH.ld"
   

4. Execute the script and select the slot you want to flash to:

   Which slot do you want to flash the image into?
   A - Slot A
   B - Slot B
   Enter your choice (A/B):
   

5. Modify the code in hr_app.c as follows:

   #if (BLE_CFG_OTA_REBOOT_CHAR != 0)
       case HRS_STM_BOOT_REQUEST_EVT:
   /* USER CODE BEGIN HRS_STM_BOOT_REQUEST_EVT */
           uint8_t start_address_sector = (*(uint8_t*)(SRAM1_BASE+3));
           *(uint32_t*)SRAM1_BASE = *(uint32_t*)pNotification->DataTransfered.pPayload;
           (*(uint8_t*)(SRAM1_BASE+3)) = start_address_sector;
           NVIC_SystemReset();
   /* USER CODE END HRS_STM_BOOT_REQUEST_EVT */
           break;
   #endif

6. Build the project and locate the binary file under the Debug folder.