Write initial values to flash during production

[nrbrook]

During production we need to provision each device with some custom data that must last the life time of the device, ideally using nrfjprog. What is the best way to do this? I see there are Customer registers in UICR, but what about writing more than 32 bytes?

[Nguyen Hoan Hoang]

You could reserve a section flash at a fixed location in your firmware and write the custom data directly to that address with an external utility such as the nrfjprog. 

[nrbrook]

How would you reserve the flash and avoid FDS and the boot loader (when performing DFU) writing to it?

[Nguyen Hoan Hoang]

You declare a new section in both your firmware global variable and in the linker script map it to an fixed address

[Jimmy Wong]

HI,

You can prepare the batch script to write on the UICR through nrfjprog command.

such as

https://jimmywongbluetooth.wordpress.com/2019/09/16/how-to-store-the-custom-address-device-name-and-device-id-on-nrf52-series/

https://jimmywongbluetooth.wordpress.com/2019/08/19/manufacturer-storage-data-on-uicr-region/

or

You can generate the binary file and use the objcopy 

objcopy -v -I binary -O ihex --change-addresses 0x12000000 IMAGE_01.bin IMAGE_01.hex

and then use the nrfjprog to program the hex file on specify address

nrfjprog -f nrf52 --qspicustominit --program ..\result_output\IMAGE_01.hex  --sectorerase

similar to the QSPI https://jimmywongbluetooth.wordpress.com/2019/10/09/how-to-store-the-file-inside-the-qspi-flash/

[nrbrook]

I determined that as a whole page must be erased before flash can be written, the fixed address storage size must be a multiple of the page size (0x1000).

So far I've got, in my linker file:

MEMORY
{
    /* MBR_FLASH (rx)        : ORIGIN = 0x00000000, LENGTH = 0x00001000 */
    /* SOFTDEVICE_FLASH (rx) : ORIGIN = 0x00001000, LENGTH = 0x00025000 */

    FLASH (rx)               : ORIGIN = 0x00026000, LENGTH = 0x00051000
    RAM (rwx)                : ORIGIN = 0x20003320, LENGTH = 0x0000cce0

    provisioning_data (rwx)  : ORIGIN = 0x00077000, LENGTH = 0x00001000

    /* BOOTLOADER_FLASH (rx) : ORIGIN 0x00078000, LENGTH = 0x00006000 */
}

SECTIONS
{
  .provisioning_data_block 0x00077000 :
  {
    KEEP(*(.provisioning_data_sect))
  } > provisioning_data
}

...

Here I reduced the size of the application flash by 0x1000 and added a new block of data at the end of the application flash. Then I define the section.

As I'm using FDS, I needed to reserve the flash from being used by FDS in sdk_config.h:

#define FDS_VIRTUAL_PAGES_RESERVED 1

Then, in my code:

uint8_t __attribute__((section (".provisioning_data_sect"))) m_provisioning_data[0x1000] __attribute__((used));
const uint32_t provisioningStart = 0xA55A5AA5;

...

if(*(uint32_t *)m_provisioning_data != provisioningStart) {
    nrf_nvmc_page_erase(m_provisioning_data);
    nrf_nvmc_write_word(m_provisioning_data, provisioningStart);
}

nrf_nvmc_write_byte(m_provisioning_data + 4, 0xBA);

NRF_LOG_INFO("0x%08X", m_provisioning_data);
NRF_LOG_HEXDUMP_INFO(m_provisioning_data, 5)

Is this correct so far?

Is this sufficient to protect the flash from being overwritten by the bootloader etc? I would assume not, since I have not modified any sizes in the (DFU BLE) bootloader. What would I need to modify?