I think there is a detailed discussion as to what is supposed to be inside the cape EEPROMs in the "BeagleBone Black System Reference Manual"
It looks like there is a live Wiki version at https://github.com/beagleboard/beaglebone-black/wiki/System-Reference-Manual But since that address has already been reserved by the kernel, for the cape manager, you will not be able to read/write it from user space. If you want to access that address from user space on a BBB, you need to stop the cape manager. Google "BBB without reserved I2C addresses" on this forum. and look at "am335x-bone-common-no-capemgr.dtsi" --- Graham == On Wed, Oct 31, 2018 at 10:01 AM MG <musta...@braingrid.io> wrote: > @Graham I do have a cape with EEPROM at address 0x57 but the EEPROM is > wiped with nothing on it so I guess that is why the board doesn't populate > that address by default. How can I fix that? > > On Tuesday, October 30, 2018 at 11:14:50 PM UTC-4, gra...@flex-radio.com > wrote: >> >> Those addresses at 0x54-0x57 are reserved by the kernel driver. >> >> Unless you have some capes with those EEPROMS populated, there is nothing >> actually there. >> >> --- Graham >> >> == >> >> On Tuesday, October 30, 2018 at 7:01:27 PM UTC-5, MG wrote: >>> >>> The BeagleBoneBlack comes with an "internal" EEPROM connected to i2c-0 >>> line. I can see that clearly when I do i2cdetect: >>> >>> debian@beaglebone:~$ i2cdetect -y -r 0 >>> 0 1 2 3 4 5 6 7 8 9 a b c d e f >>> 00: -- -- -- -- -- -- -- -- -- -- -- -- -- >>> 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- >>> 20: -- -- -- -- UU -- -- -- -- -- -- -- -- -- -- -- >>> 30: -- -- -- -- UU -- -- -- -- -- -- -- -- -- -- -- >>> 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- >>> 50: UU -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- >>> 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- >>> 70: UU -- -- -- -- -- -- -- >>> >>> It is showing under address 0x50. When I try to do ahexdump I get the >>> following values with no issue: >>> >>> sudo hexdump -C /sys/class/i2c-dev/i2c-0/device/0-0050/eeprom | head >>> -5 >>> 00000000 aa 55 33 ee 41 33 33 35 42 4e 4c 54 30 30 30 43 >>> |.U3.A335BNLT000C| >>> 00000010 31 38 33 37 42 42 42 47 30 36 32 32 ff ff ff ff >>> |1837BBBG0622....| >>> 00000020 ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff >>> |................| >>> * >>> 00001000 aa 55 33 ee 41 33 33 35 42 4e 4c 54 30 30 30 43 >>> |.U3.A335BNLT000C| >>> >>> Now I want to add another EEPROM (with cape) on i2c-2 line which is >>> supported according to [BBB SRM]( >>> https://cdn-shop.adafruit.com/datasheets/BBB_SRM.pdf) section 8.2. It >>> is the CAT24C256 as mentioned in the SRM. The allowable address range for >>> the expansion cards is 0x54-0x57. When I do i2cdetect I can see the >>> following: >>> >>> debian@beaglebone:~$ i2cdetect -r -y 2 >>> 0 1 2 3 4 5 6 7 8 9 a b c d e f >>> 00: -- -- -- -- -- -- -- -- -- -- -- -- -- >>> 10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- >>> 20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- >>> 30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- >>> 40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- >>> 50: -- -- -- -- UU UU UU UU -- -- -- -- -- -- -- -- >>> 60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- >>> 70: -- -- -- -- -- -- -- -- >>> >>> I can see the addresses 0x54-0x57 showing, but when I try hex dump I get >>> an error: >>> >>> hexdump: /sys/class/i2c-dev/i2c-2/device/2-0054/eeprom: Connection >>> timed out >>> >>> Questions: >>> >>> 1. Why are they showing as U's not actual address numbers? I know U >>> stands for used resource? >>> 2. Why am I failing to read from that EEPROM? I have tried all addreses >>> from 0x54-0x57 with no luck. I can confirm that those addresses are showing >>> in /sys/class/i2c-dev/i2c-2/device and the each dir has the following in it: >>> >>> debian@beaglebone:~$ ls >>> /sys/class/i2c-dev/i2c-2/device/2-0054/ -la >>> total 0 >>> drwxr-xr-x 4 root root 0 Oct 26 19:46 . >>> drwxr-xr-x 8 root root 0 Oct 26 19:46 .. >>> drwxr-xr-x 3 root root 0 Oct 26 19:47 2-00540 >>> lrwxrwxrwx 1 root root 0 Oct 26 19:47 driver -> >>> ../../../../../../bus/i2c/drivers/at24 >>> -rw------- 1 root root 32768 Oct 26 19:47 eeprom >>> -r--r--r-- 1 root root 4096 Oct 26 19:47 modalias >>> -r--r--r-- 1 root root 4096 Oct 26 19:47 name >>> lrwxrwxrwx 1 root root 0 Oct 26 19:47 of_node -> >>> ../../../../../../firmware/devicetree/base/ocp/i2c@4819c000 >>> /cape_eeprom0@54 >>> drwxr-xr-x 2 root root 0 Oct 26 19:47 power >>> lrwxrwxrwx 1 root root 0 Oct 26 19:47 subsystem -> >>> ../../../../../../bus/i2c >>> -rw-r--r-- 1 root root 4096 Oct 26 19:47 uevent >>> >>> I can see the addresses mapping into the kernel but when I try to >>> hexdump eeprom it doesn't work at all. I though this was supposed to be >>> setup by kernel since it is mentioned in BeagleBone SRM. Am I going to need >>> an overlay to add to uboot for this? It doesn't make sense since i2c-2 is >>> already set up by default i.e. when I connect another device at address >>> aside from 0x54-0x57 it shows up fine and I'm able to interface to it? >>> >>> All I'm trying to do is read from the EEPROM like I did with the >>> "internal" one to confirm it is working. What am I doing wrong? >>> >> -- > For more options, visit http://beagleboard.org/discuss > --- > You received this message because you are subscribed to a topic in the > Google Groups "BeagleBoard" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/beagleboard/r_cnUtBakj4/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > beagleboard+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/5152cbd8-5ca5-499c-b93f-d57ee2a85c79%40googlegroups.com > <https://groups.google.com/d/msgid/beagleboard/5152cbd8-5ca5-499c-b93f-d57ee2a85c79%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. 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