1.8 PRIME Service Bootloader

• Non-volatile data storage. The PRIME Service Bootloader needs it to manage the bootloading process and the boot configuration.
  • For PIC32CXMT it is implemented using the User Signature.

    static void lAPP_BOOTLOADER_UpdateUserSignature(uint8_t pagesCnt, BOOT_STATE state) 
    {
        /* Update values */
        bootConfig[16] = pagesCnt;
        bootConfig[17] = (uint8_t) state;
    
        /* Erase the user signature */
        SEFC0_UserSignatureErase(BOOT_USER_SIGNATURE_BLOCK);
    
        /* Update the user signature */
        (void) SEFC0_UserSignatureWrite((void*) userSignBuf,
                (uint32_t) BOOT_USER_SIGNATURE_SIZE_64,
                (SEFC_USERSIGNATURE_BLOCK) BOOT_USER_SIGNATURE_BLOCK,
                (SEFC_USERSIGNATURE_PAGE) BOOT_USER_SIGNATURE_PAGE);
    }

• Memory handling. The PRIME Service Bootloader needs to delete, copy and verify pages.
  • For PIC32CXMTG it is implemented using the SEFC0 peripheral.

    static uint8_t lAPP_BOOTLOADER_DeletePage(uint32_t addr) 
    {
        SEFC0_RegionUnlock(addr);
    
        while (SEFC0_IsBusy()) {
            ;
        }
    
        SEFC0_PageErase(addr); // Function erases 16 pages
    
        while (SEFC0_IsBusy()) {
            ;
        }
    
        return 1;
    }
    
    static uint8_t lAPP_BOOTLOADER_CopyPage(uint32_t srcAddr, uint32_t dstAddr) 
    {
        uint8_t *page;
        uint8_t i;
    
        (void) memcpy(pageBlock, (uint8_t *) (srcAddr), BOOT_FLASH_16PAGE_SIZE);
        page = &pageBlock[0];
    
        for (i = 0; i < BOOT_FLASH_PAGES_NUMBER; i++) {
            if (SEFC0_PageWrite((uint32_t *) page, dstAddr) == false) {
                return 0;
            }
    
            while (SEFC0_IsBusy()) {
                ;
            }
    
            page += BOOT_FLASH_PAGE_SIZE;
            dstAddr += BOOT_FLASH_PAGE_SIZE;
        }
    
        return 1;
    }
    
    static uint8_t lAPP_BOOTLOADER_VerifyPage(uint8_t *ramPage, uint8_t *flashPage, uint16_t pageSize) 
    {
        uint16_t i = 0;
    
        while (i < pageSize) {
            if (ramPage[i] != flashPage[i]) {
                return 0;
            }
    
            i++;
        }
    
        return 1;
    }

case APP_BOOTLOADER_STATE_INIT:
{
    bool appInitialized = true;

    if (appInitialized) {
        /* Ensure all priority bits are assigned as preemption */
        /* priority bits. */
        NVIC_SetPriorityGrouping(__NVIC_PRIO_BITS);
        __set_BASEPRI(0);

        /* Disable User Signature write protection */
        SEFC0_WriteProtectionSet(0);

        /* Enable write and read User Signature rights */
        /* (block 0 / area 1)  */
        SEFC0_UserSignatureRightsSet(
                SEFC_EEFC_USR_RDENUSB1_Msk | SEFC_EEFC_USR_WRENUSB1_Msk);

        app_bootloaderData.state = APP_BOOTLOADER_STATE_SERVICE_TASKS;
    }

    break;
}

• Extract the boot configuration from the User Signature:

  /* Read the boot configuration from user signature */
  (void) SEFC0_UserSignatureRead((void*) userSignBuf,
          (uint32_t) BOOT_USER_SIGNATURE_SIZE_64,
          (SEFC_USERSIGNATURE_BLOCK) BOOT_USER_SIGNATURE_BLOCK,
          (SEFC_USERSIGNATURE_PAGE) BOOT_USER_SIGNATURE_PAGE);
  
  /* Get boot configuration */
  bootConfig = userSignBuf + BOOT_CONFIG_OFFSET_USER_SIGN;
  cfgKey = ((uint32_t) bootConfig[3]) << 24;
  cfgKey += ((uint32_t) bootConfig[2]) << 16;
  cfgKey += ((uint32_t) bootConfig[1]) << 8;
  cfgKey += (uint32_t) bootConfig[0];

• Extract the boot information, if the boot configuration is valid:

   /* Get boot information */
  imageSize = (uint32_t) (bootConfig[7]) << 24;
  imageSize += (uint32_t) (bootConfig[6]) << 16;
  imageSize += (uint32_t) (bootConfig[5]) << 8;
  imageSize += (uint32_t) (bootConfig[4]);
  origAddr = (uint32_t) (bootConfig[11]) << 24;
  origAddr += (uint32_t) (bootConfig[10]) << 16;
  origAddr += (uint32_t) (bootConfig[9]) << 8;
  origAddr += (uint32_t) (bootConfig[8]);
  destAddr = (uint32_t) (bootConfig[15]) << 24;
  destAddr += (uint32_t) (bootConfig[14]) << 16;
  destAddr += (uint32_t) (bootConfig[13]) << 8;
  destAddr += (uint32_t) (bootConfig[12]);
  pagesCounter = bootConfig[16];
  bootState = bootConfig[17];

• Trigger the firmware swap, if needed:

  /* Check if swap fw is needed. If not, load defaults. */
  if (lAPP_BOOTLOADER_IsSwapCmd(imageSize, origAddr,
          destAddr) == true) {
      /* Swap fw */
      (void) lAPP_BOOTLOADER_SwapFwVersion(imageSize,
              origAddr,
              destAddr);
  
      /* Clear boot configuration (leave configuration key) */
      (void) memset(&bootConfig[4], 0, 16);
  
      /* Update user signature */
      lAPP_BOOTLOADER_UpdateUserSignature(0, BOOT_IDLE);
  }

• Start the user application:

  /* Set the stack pointer to the start of the firmware application */
  __set_MSP(*(int *) (BOOT_FLASH_APP_FIRMWARE_START_ADDRESS));
  
  /* Offset the start of the vector table (first 6 bits must be 
   * zero) */
  /* The register containing the offset, from 0x00000000, is at 
   * 0xE000ED08 */
  SCB->VTOR = ((uint32_t) BOOT_FLASH_APP_FIRMWARE_START_ADDRESS &
          SCB_VTOR_TBLOFF_Msk);
  __DSB();
  __ISB();
  __enable_irq();
  /* * (int *) 0xE000ED08 = FIRMWARE_START_ADDRESS; */
  
  /* Jump to the start of the firmware, casting the address as 
   * function pointer to the start of the firmware. We want to jump 
   * to the address of the reset. */
  
  /* Handler function, that is the value that is being pointed at 
   * position FIRMWARE_RESET_ADDRESS */
  
  void (*runFirmware)(void) = NULL;
  runFirmware = (void (*)(void))(*(uint32_t *)
          BOOT_FLASH_APP_FIRMWARE_RESET_ADDRESS);
  runFirmware();
  
  while (1) {
      ;
  }