Graham, I do not think he's talking about the on board eeprom.
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." > But even if he is, the SRM says: 32k right on page 30: *5.3.2 32KB EEPROM* It also says 2G eMMC so it has to be in relationto a Rev A, or Rev B. However . . .since no ones asked, or mentioned the board revision number . . . On Fri, Jul 15, 2016 at 11:16 AM, Graham <[email protected]> wrote: > 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 >>>>> >>>>> -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to the Google Groups > "BeagleBoard" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/38c05665-c281-4cb2-a438-c133a39e2d5a%40googlegroups.com > <https://groups.google.com/d/msgid/beagleboard/38c05665-c281-4cb2-a438-c133a39e2d5a%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > For more options, visit https://groups.google.com/d/optout. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CALHSORrTZEBo4W2NwjMPb-kYH3%2BBdG6rq8y17OGvqN-b0ddY3Q%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
