Custom DFU Process

[wrani]

Hi 

I have implemented a custom DFU process, where NRF52840 sends another NRF52833 an image to program. 

The NRF52833  receives the image and validates CRC, if all OK , I am performing the following in my application : 

#define BOOTLOADER_SETTINGS_PAGE_ADDR (0x0007F000)
#define BOOTLOADER_SETTINGS_PAGE_PTR ((uint8_t*)BOOTLOADER_SETTINGS_PAGE_ADDR)

#define IMAGE_UPDATE_ADDRESS (0x00048000)
#define IMAGE_UPDATE_ADDRESS_PTR ((uint8_t*)IMAGE_UPDATE_ADDRESS)
#define BOOTLOADER_BACKUP_SETTINGS_PAGE_ADDR (0x0007E000)
#define BOOTLOADER_BACKUP_SETTINGS_PAGE_ADDR_PTR ((uint8_t*)BOOTLOADER_BACKUP_SETTINGS_PAGE_ADDR)

void apply_firmware(uint32_t length,uint32_t crc)
{
   ret_code_t ret;
  /********************************************************************
  if enter dfu , stop other Tasks here to make sure update successful
*********************************************************************/
ret = nrf_sdh_disable_request();
vTaskDelay(2000);
memcpy((void *)&s_dfu_settings, BOOTLOADER_BACKUP_SETTINGS_PAGE_ADDR_PTR, sizeof(nrf_dfu_settings_t));
s_dfu_settings.bank_1.bank_code = NRF_DFU_BANK_VALID_APP;
s_dfu_settings.bank_0.bank_code = NRF_DFU_BANK_INVALID;
s_dfu_settings.bank_1.image_crc = crc32_compute(IMAGE_UPDATE_ADDRESS_PTR , length, NULL);
s_dfu_settings.bank_1.image_size = length;
s_dfu_settings.progress.update_start_address = IMAGE_UPDATE_ADDRESS;
s_dfu_settings.write_offset = 0;

s_dfu_settings.crc = crc32_compute((uint8_t*)(&s_dfu_settings) + 4, DFU_SETTINGS_INIT_COMMAND_OFFSET - 4, NULL);
//write back to flash
nrf_nvmc_page_erase(BOOTLOADER_SETTINGS_PAGE_ADDR);
vTaskDelay(2000);
nrf_nvmc_write_bytes(BOOTLOADER_SETTINGS_PAGE_ADDR, (uint8_t *)(&s_dfu_settings), sizeof(s_dfu_settings));
vTaskDelay(2000);

NVIC_SystemReset();
}

This works, only if I modify the following in bootloader code ( nrf_dfu_settings.c ) :

void nrf_dfu_settings_reinit(void)
{
 bool settings_valid = settings_crc_ok();
 bool settings_backup_valid = settings_backup_crc_ok();
 settings_backup_valid = false;

....

}

Unless I do so , the backup settings page will be copied to the settings page : 

void nrf_dfu_settings_reinit(void)
{
  bool settings_valid = settings_crc_ok();
  bool settings_backup_valid = settings_backup_crc_ok();
  if (settings_valid)
  { 
    NRF_LOG_DEBUG("Using settings page.");
    memcpy(&s_dfu_settings, m_dfu_settings_buffer, sizeof(nrf_dfu_settings_t));
    if (settings_backup_valid)
    {
      NRF_LOG_DEBUG("Copying forbidden parts from backup page.");
      settings_forbidden_parts_copy_from_backup((uint8_t *)&s_dfu_settings);
    }
}

...

How can I avoid the call to "settings_forbidden_parts_copy_from_backup" ? I have tried to erase the BACKUP_SETTING page ( 0xfe000) but it is protected 

https://devzone.nordicsemi.com/f/nordic-q-a/47147/erasing-of-master-boot-record-parameters-page-hangs

[Vidar Berg]

Hi,

This implementation is made to limit what parameters the app is allowed to change inside the settings page. If your bootloader is built with NRF_BL_DFU_ALLOW_UPDATE_FROM_APP you are allowed to change the fields highlighted below.

Does your custom DFU process include the init command like in our DFU solution? If not, I'm afraid you will have to modify the bootloader module as you have done already.

[wrani]

Thanks. 

So once I'll set NRF_BL_DFU_ALLOW_UPDATE_FROM_APP  , how to I change my code above to allow DFU successful completion ? 

[Vidar Berg]

You need to change the implementation above so that instead of updating .bank0/1 directly, you store the init_command. The bootloader will take of updating the other fields during the FW activation process afterwards.  

[wrani]

Thanks, Any example I can use as a reference for using init_command in an application ? 

[Vidar Berg]

I made an example that handles DFU in the application layer a while ago which you can find here: https://devzone.nordicsemi.com/f/nordic-q-a/46994/background-dfu-application-source-code/187534#187534.  But note that's it's using the existing SDK DFU modules to receive and store the init packet.