Saving words in FDS memory ?

Question

I was able to use the fds with the help of good people here , I am trying now to save a word into memory.

As I see in the docs, the only way to save data is by uint32_t chunks .

So I guess I am doing it wrong but I am trying this without success :

to save with this :

        char data[]="lola"; 
        uint32_t save;
        memcpy(&save, data, 4);


        #define FILE_ID     0x1111
	#define REC_KEY     0x2222

	fds_record_t        record;
	fds_record_desc_t   record_desc;
	fds_record_chunk_t  record_chunk;
	// Set up data.
	record_chunk.p_data         = &save;
       record_chunk.length_words   = 1;
	// Set up record.
	record.file_id              = FILE_ID;
	record.key              		= REC_KEY;
	record.data.p_chunks       = &record_chunk;
	record.data.num_chunks   = 1;
	
    ....

Then to read with :

... //some code that works , then
			 data = (uint32_t *) flash_record.p_data;
			for (uint8_t i=0;i<flash_record.p_header->tl.length_words;i++)
			{
                                   char bytes[6];
                                   char n =  data[i];
                                   bytes[0] = (n >> 24) & 0xFF;
                                   bytes[1] = (n >> 16) & 0xFF;
                                   bytes[2] = (n >> 8) & 0xFF;
                                   bytes[3] = n & 0xFF;
                                   for (int k=0;k<4;k++)
                                       NRF_LOG_INFO("message is: %c ",bytes[k]);

				//NRF_LOG_INFO("record ID: %d and data: %x ",record_desc.record_id,data[i]);

			
			}

Which will print record 1 and data - means empty data

Is this the way to save a word ?
what about saving multiple words like this ? is it a overhead ?

Thanks !

FormerMember · Accepted Answer

The below code shows how to store and retrieve a string using FDS: 
 static ret_code_t fds_test_write(void)
{
	#define FILE_ID 0x1111
	#define REC_KEY 0x2222
	
	static char const my_text[] = "What a day, what a day!";
	
	fds_record_t record;
	fds_record_desc_t record_desc;
	fds_record_chunk_t record_chunk;
	// Set up data.
	record_chunk.p_data = my_text; 
	record_chunk.length_words = (sizeof(my_text)+3)/4; // When calculating the length in words, using integer division, the result will always be "rounded" down to the whole integer. A data array of 21 bytes, is strictly speaking 5 words + 1 byte. However, the length should be in words, and thus 6 words are needed to store all the data. 21/4 = 5, (21+3)/4 = 6. For 20 bytes, 5 words are needed, in integer division 20/4 = (20+3)/4 =5.
	// 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_INFO("Writing Record ID = %d 
",record_desc.record_id);
	return NRF_SUCCESS;
}

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
	
	char *p_data;
	uint32_t err_code;
	
	NRF_LOG_INFO("Start searching... 
");
	// 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_INFO("Found Record ID = %d
",record_desc.record_id);
 NRF_LOG_INFO("Data = ");
 
 // Access the record through the flash_record structure.
 p_data = (char *) flash_record.p_data;
 NRF_LOG_INFO(" %s 
", (uint32_t)p_data);
 
 
 // Close the record when done.
 err_code = fds_record_close(&record_desc);
 if (err_code != FDS_SUCCESS)
 {
 return err_code;	
 }
	}
	return NRF_SUCCESS;
	
}

Saving words in FDS memory ?

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