Beaglebone Green I2C

I started working with the Exadler DMCC and a Beaglebone Black for a motor control application and it is working OK. I bought some BBG’s as they are neater for what I am doing (we don’t need a power connector or HDMI) but the I2C won’t work. There are actually 2 I2C boards added to the BBB. I2C detects them on the BBB but not the BBG.

The results for i2cdetect are below. I have tried mutliple BBG’s with the same result.

Working unit (Beaglebone black)

root@beaglebone:/Development/BBBB# i2cdetect -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 – -- – -- – -- –

The one that won’t work (Beaglebone Green)

root@beaglebone:/Development/BBBB# i2cdetect -r 0

0 1 2 3 4 5 6 7 8 9 a b c d e f

00: – -- – -- – -- – -- – -- – -- –

10: – -- – -- – -- – -- – -- – -- – -- – --

20: – -- – -- UU – -- – -- – -- – -- – -- –

30: – -- – -- – -- – -- – -- – -- – -- – --

40: – -- – -- – -- – -- – -- – -- – -- – --

50: UU – -- – -- – -- – -- – -- – -- – -- –

60: – -- – -- – -- – -- – -- – -- – -- – --

70: – -- – -- – -- – --

Does any one have any suggestions for the cause?

So random potentially-not-helpful-but-maybe-so advice:

UUs indicate that the kernel is using that address, via some module.
So, on your BBB perhaps it's a cape and the module was loaded? UUs I
think, don't necessarily guarantee you have a device there, just that
kernel has loaded a module that's claimed that address (I might be
wrong on this).

But presumably, by "work" you mean that the i2c device (what is it?)
actually works on the BBB besides just showing up?

Also, maybe check a different i2c bus? i.e. do i2c-detect on -r 1/2 etc...

To which I2C bus do you think you hooked the external I2C chips? (Hint: there are three of them, and bus 0 is not pinned out to the outside world.)
What pins are you using?
Did you put I2C pull-up resistors to +3.3V out at the chips?
Which version of the OS and kernel are you using? (The I2C buses were renumbered.)
But in no case is I2C bus 0 appropriate for the user, that is for on-board control of the power supply and video chips, etc. It is not brought out to P8/P9 where you can get at it.
The reason I2C bus 0 looks different between a BBB and BBG is that the HDMI chip does not exist on the BBG.

— Graham