Set up expansion EEPROM i2c-2 BeagleBoneBlack Rev-C - beagleboneblack

Question

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 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:
Why are they showing as U's not actual address numbers? I know U stands for used resource?
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?
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?

Answer 1

The issue was that the cape manager was "hogging" those addresses on i23c-2. We will need to disable the cape manager in order to free those addresses. After doing that it shows 0x57 under i2c-2 so it should work afterwards.
Please checkout the following link as to how to disable Cape Manager on BeagleBone:
https://groups.google.com/forum/?utm_medium=email&utm_source=footer#!msg/beagleboard/NG8cDWuv2Y0/69vk5F5ZAgAJ)
Make sure to edit the am335x-boneblack-uboot.dts file remove the include on line 11 and replace with the following:
#include "am335x-bone-common-no-capemgr.dtsi"
Note this will disable your i2c-2 line by default so either enable it via overlays or edit the am335x-bone-common-no-capemgr.dtsi & add after &i2c0 (around line 245):
&i2c2 {
pinctrl-names = "default";
pinctrl-0 = <&i2c2_pins>;
status = "okay";
clock-frequency = <100000>;
};