Saving words in FDS memory ?

RE: Saving words in FDS memory ?

kiranj — Wed, 19 Dec 2018 07:24:11 GMT

I am not able to store the whole string as in my_text[] = "What a day, what a day!";its giving error at time of writing,please help??

RE: Saving words in FDS memory ?

Lola — Fri, 26 May 2017 09:14:13 GMT

Thank you !

RE: Saving words in FDS memory ?

FormerMember — Fri, 26 May 2017 07:02:49 GMT

my_text is an array, and an array variable is a variable that holds the address of the first element in the array. Therefore, record_chunk.p_data can be assigned to my_text one of the following ways, and they are equivalent:

record_chunk.p_data = my_text;
record_chunk.p_data = &my_text[0];

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.

Yes, my_text should be defined the following way: static char const my_text[] = ...

RE: Saving words in FDS memory ?

Lola — Wed, 24 May 2017 19:20:33 GMT

By the way, I found out that the word you are about to save must be static, or global otherwise the system just lose it while it's writing, and you read garbage. So If I drop the static I get garbage, if I add it it's good. Also, if I set the my_text to be global and not static it's also work.

RE: Saving words in FDS memory ?

Lola — Wed, 24 May 2017 19:17:25 GMT

Thanks a lot, did you mean record_chunk.p_data= &my_text (with the address sign) ? it's a pointer that should get an address no ?

Also, why calculating the size with the 3/4 ?

RE: Saving words in FDS memory ?

FormerMember — Wed, 24 May 2017 13:03:50 GMT

I have updated the code to show how to store and retrieve a string.

RE: Saving words in FDS memory ?

Lola — Wed, 24 May 2017 06:54:10 GMT

Hi, Kristen thanks a lot, but it wasn't my question - that I already know. The question was how to save strings(char arrays), and read them. You can see in the first 3 lines of the question I am trying to save a string into memory as a set of Uint32 .

RE: Saving words in FDS memory ?

FormerMember — Wed, 24 May 2017 06:26:29 GMT

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 \r\n",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... \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_INFO("Found Record ID = %d\r\n",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 \r\n", (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;
	
}