Are the docs you are using up to date?
Reading the current SRM, (Version C.1) section 5.3.2 says that there is a
single 4K Byte EEPROM on board the Beaglebone.
They mumble something about there having been a cost reduction. :-)
--- Graham
==
On Friday, July 15, 2016 at 1:08:27 PM UTC-5, Graham wrote:
>
> OK. In that case it is a 32k Byte part.
> --- Graham
>
> ==
>
> On Friday, July 15, 2016 at 12:37:20 PM UTC-5, Bryan Wilcutt wrote:
>>
>> Graham,
>> The part number is AT24c256 and a quick jot over to Atmel's trusty
>> website and I found the spec sheet... "256K Serial Eeprom... organized as
>> 512 pages of 64 bytes each."
>>
>> So, that should mean 512x64 = 32,768 bytes... .32K.
>> 256k bits = 262,144 / 8 = 32,768 bytes... 32k.
>>
>> It's most certainly a 32k-byte part.
>>
>> Thanks,
>> Bryan
>>
>> On Friday, July 15, 2016 at 11:45:02 AM UTC-5, Graham wrote:
>>
>>> Brian:
>>>
>>> You need to learn to speak "marketing" and "binary".
>>>
>>> A 32 k EEPROM (named by marketing) is a 32k BIT EEPROM.
>>>
>>> 32k BITs divided by 8 bits-per-byte is 4k BYTES.
>>>
>>> 4k BYTES is 0x1000 BYTES.
>>>
>>> So, your address space wraps around every 0x1000 BYTES.
>>>
>>> The data is not repeated every 0x1000 bytes, it is the SAME data.
>>>
>>> Sounds like your EEPROM is working just fine.
>>>
>>> --- Graham
>>>
>>> ==
>>>
>>> On Friday, July 15, 2016 at 10:47:54 AM UTC-5, Bryan Wilcutt wrote:
>>>>
>>>> I've been playing with the BBB 32k eeprom by reading and writing data
>>>> to it. I use fseek(), fopen(), fread() and fwrite(). The device I am
>>>> reading/writing/opening is:
>>>> /sys/bus/i2c/devices/0-0050/at24-0/nvmem
>>>>
>>>> This does seem to work however not well. I noticed that the same data
>>>> is repeated every 0x1000 bytes. Why is that? Am I not addressing the
>>>> part
>>>> correctly? Since I'm ultimately using the at24.c driver, I inspected it
>>>> and it does seem to attempt to translate addresses for the part. Are
>>>> there
>>>> specific limitations with at24 that I should be aware of, nothing seems to
>>>> be documented that I've seen.
>>>>
>>>> #define e2FILE "/sys/bus/i2c/devices/0-0050/at24-0/nvmem"
>>>>
>>>> int readEEPROMAt(unsigned char *p, unsigned int startAddr, unsigned
>>>> int len)
>>>> {
>>>> int retVal = 0;
>>>> FILE *fp = NULL;
>>>>
>>>> if ((fp = fopen(e2FILE, "r")) != NULL)
>>>> {
>>>> if (fseek(fp, startAddr, 0) == 0)
>>>> {
>>>> if (fread(p, 1, len, fp) != len)
>>>> printf("Error: Cannot read EEPROM\n");
>>>> else
>>>> retVal = 1;
>>>> } else {
>>>> printf("Error: Could not index EEPROM, no data read.");
>>>> }
>>>> } else {
>>>> printf("Error: Cannot open EEPROM\n");
>>>> }
>>>>
>>>> if (fp)
>>>> fclose(fp);
>>>>
>>>> return retVal;
>>>> }
>>>>
>>>> Bryan
>>>>
>>>>
--
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