nrf9160 Flash access

[Randall]

Hi.  I need to use some of the flash on the nRF9160 for non-volatile storage.  But I want to do it in a very specific way to save on RAM usage.

Essentially I want to be able to define a character array like;

const char configInformation[32768];

I want to be able to use flash functions to erase and write the data block

flash_erase( device, configInformation);

offset = 0;

loop until configInformation done

     flash_write( device, &configInformation[offset], newData, sizeof(newData) );

     offset += sizeof(newData)

(please excuse the pseudo code, I'm just trying to get a concept accross)

Then I'd like to be able to access configInformation in a bytewise fashion without using a read  function to stuff pieces of it into a RAM buffer.

I'm reading through the flash driver or the non-volatile storage subsystems and they don't seem to provide this functionality.  Is there a way to do this?

Thankss

[Heidi]

Hi! I'm sorry for not replying sooner. I just wanted to let you know I'm looking into this and I'll update the case when I have some information for you.

Best regards,

Heidi

[Randall]

I guess I should have replied when I figured it out for myself.  With no replies I didn't know if people weren't interested or it was so simple people thought I was an idiot for asking.  Because solution was pretty simple.  Maybe people could critique my solution.

Anyway, standard nrf9160 definition includes a scratchpad and storage flash partition.  Although one could also define their own, I'm going to example using the scratchpad partition.

I create a pointer to constant data;

const char * scratchData;

As well as some defines for access to the scratch area;

#define FLASH_OFFSET            DT_FLASH_AREA_IMAGE_SCRATCH_OFFSET
#define FLASH_PAGE_SIZE      DT_FLASH_ERASE_BLOCK_SIZE
#define FLASH_SIZE                  DT_FLASH_AREA_IMAGE_SCRATCH_SIZE

When I initialize, I assign this to the scratchpad partition; as well as getting a device object for the flash;

flashDev = device_get_binding( DT_FLASH_DEV_NAME );

scratchData = (char *)FLASH_OFFSET;

When I erase/write to the section, I use the flash functions

// Erase

flash_write_protection_set( flashDev, false );
flash_erase( flashDev, FLASH_OFFSET, FLASH_PAGE_SIZE );
flash_write_protection_set( flashDev, true );

// Write Block

if (blockOffset + blockSize) > FLASH_SIZE )
{
  LOG_ERR( "Write Exceeds Scratchpad Size" );
  return(-1);
}

blockOffset += FLASH_OFFSET;
flash_write_protection_set( flashDev, false );
flash_write( flashDev, blockOffset, blockData, blockSize );
flash_write_protection_set( flashDev, true );

Then I can access the block using the scratchData pointer.  I use the following configuration variables in prj.conf;

CONFIG_FLASH=y
CONFIG_FLASH_PAGE_LAYOUT=y
CONFIG_MPU_ALLOW_FLASH_WRITE=y
CONFIG_SOC_FLASH_NRF=y
CONFIG_SOC_FLASH_NRF_EMULATE_ONE_BYTE_WRITE_ACCESS=y

The emulate byte access is so that I can write generic data.  I'm not worried about the extra overhead.  If you want to handle 4-byte alignment yourself, you don't have to include this.

I deleted a lot of the error handling from my code to make the concept easier to see.

Thanks,