Bootloader address flash write

[AP1]

1. Hi i am utilizing nrf52840 sdk with ver 17.1.10 s140 and i have the central UART as main app from there we are calling bootloader

2. Before calling bootloader ble dfu we are writing the data in the Flash address 0x3e000 4 bytes

3. After entering into bootloader ble dfu mode the flash address 0x3e000  data is FF 

4.  which flash address i can write so that the value remains  even it enters into ble bootloader dfu 

5. for flash writing i am using fstorage funcions   in the main central uart app

ret_code_t ret = nrf_fstorage_erase(&fstorage, 0x3e000, 1, NULL);

wait_for_flash_ready(&fstorage);

ret_code_t ret1 = nrf_fstorage_write(&fstorage, 0x3e000, &data_wrt, sizeof(data_wrt), NULL);

wait_for_flash_ready(&fstorage);

[Vidar Berg]

Hi,

You should use the area below the bootloader shown as "Application data" here:

https://docs.nordicsemi.com/bundle/sdk_nrf5_v17.1.0/page/lib_bootloader.html 

The size and location of this area is dependent on the start address of the bootloader and the NRF_DFU_APP_DATA_AREA_SIZE value configured in the bootloader project.

Bes regards,

Vidar

[AP1]

1. Hi I need to write in flash address but my issue is before writing anything I should erase atleast 4kB data in flash address then only I can write 

2. Is there any thing like we can erase only required bytes in flash 

[Vidar Berg]

The flash is erased in units of flash pages, which are 4kB each on the nRF52 series.