Use flash data storage to write and read back record of specific record_id

[helpme]

I am using this flash data storage as reference github.com/.../nRF52-fds-example

Running fds_test_write() below, it writes to a file specified by FILE_ID, REC_KEY but to different record_id all the time. So, when reading back, I will not know exactly which record_id to read back.

static ret_code_t fds_test_write(void)
{
		#define FILE_ID     0x1111
		#define REC_KEY     0x2222
		static uint32_t const m_deadbeef[2] = {0xDEADBEEF,0xBAADF00D};
		fds_record_t        record;
		fds_record_desc_t   record_desc;
		fds_record_chunk_t  record_chunk;
		// Set up data.
		record_chunk.p_data = m_deadbeef;
		record_chunk.length_words = 2;
		// Set up record.
		record.file_id = FILE_ID;
		record.key = REC_KEY;
		record.data.p_chunks = &record_chunk;
		record.data.num_chunks = 1;
				
		ret_code_t ret = fds_record_write(&record_desc, &record);
		if (ret != FDS_SUCCESS)
		{
				return ret;
		}
		 NRF_LOG_PRINTF("Writing Record ID = %d \r\n",record_desc.record_id);
		return NRF_SUCCESS;
}

Below is the code to read back the record. It reads back all the records belonging to FILE_ID and REC_KEY. What I will prefer is to have a write function that writes to a specific record_id and a read function that reads from a specific record_id. Something like;

write_record(FILE_ID, REC_KEY, record_id);

read_record(FILE_ID, REC_KEY, record_id);

Is this possible with SDK_11 s130 on nRF51-dk?

static ret_code_t fds_read(void)
{
		#define FILE_ID     0x1111
		#define REC_KEY     0x2222
		fds_flash_record_t  flash_record;
		fds_record_desc_t   record_desc;
		fds_find_token_t    ftok ={0};//Important, make sure you zero init the ftok token
		uint32_t *data;
		uint32_t err_code;
		
		NRF_LOG_PRINTF("Start searching... \r\n");
		// Loop until all records with the given key and file ID have been found.
		while (fds_record_find(FILE_ID, REC_KEY, &record_desc, &ftok) == FDS_SUCCESS)
		{
				err_code = fds_record_open(&record_desc, &flash_record);
				if ( err_code != FDS_SUCCESS)
				{
					return err_code;		
				}
				
				NRF_LOG_PRINTF("Found Record ID = %d\r\n",record_desc.record_id);
				NRF_LOG_PRINTF("Data = ");
				data = (uint32_t *) flash_record.p_data;
				for (uint8_t i=0;i<flash_record.p_header->tl.length_words;i++)
				{
					NRF_LOG_PRINTF("0x%8x ",data[i]);
				}
				NRF_LOG_PRINTF("\r\n");
				// Access the record through the flash_record structure.
				// Close the record when done.
				err_code = fds_record_close(&record_desc);
				if (err_code != FDS_SUCCESS)
				{
					return err_code;	
				}
		}
		return NRF_SUCCESS;
		
}

[Ole Bauck]

The record id is given by the fds module; you cannot specify this. You can only specify the file id and the record key which can be different for every record. I suggest that you read the documentation to get an understanding of how this works. See the functionality chapter for how data is stored with file id and record key.

So you can have functions like this:

write_record(FILE_ID, REC_KEY);
read_record(FILE_ID, REC_KEY);

[helpme]

Thanks. I think the trick is to find and delete every records before writing.

[awneil]

Ole Bauck said:

I suggest that you read the documentation to get an understanding of how this works.

I find the documentation quite opaque on what's going on with these so-called "Files" and "Records":

https://devzone.nordicsemi.com/f/nordic-q-a/35843/flash-data-storage-fds-what-is-the-point-of-files-and-records