Bug: nrf_nvmc_write_bytes() writes to the same 32bit word too many times for nRF52840.

[Jens S]

Hi,

In nRF5_SDK version 15.3.0_59ac345 with nRF52840, the function nrf_nvmc_write_bytes() writes to the same 32bit word too many times.

According to the datasheet:

"The same 32-bit word in the flash can only be written n WRITE number of times before a page erase must be performed."

and nrf_nvmc_write_bytes() is implemented like this:

void nrf_nvmc_write_bytes(uint32_t address, const uint8_t * src, uint32_t num_bytes)
{
    uint32_t i;
    for (i = 0; i < num_bytes; i++)
    {
       nrf_nvmc_write_byte(address + i,src[i]);
    }
}

However, for nRF52840 has Nwrite=2, so for any buffer with num_bytes>2 this function can exceed the number of writes permitted.

Instead this function should group the bytes together such that it only writes to each 32bit word once.

Thanks

[Einar Thorsrud]

Hi,

Thank you for reporting. I have forwarded this to the SDK developers.

[Mark Rages]

I just noticed this as well.  This is pretty shocking code to have in the SDK; it seems like the driver authors have not read the product specification(?)

A better implementation would be a word-aware nrf_nvmc_write_bytes(), and nrf_nvmc_write_byte() could be implemented in terms of this function (rather that the other way around).