Rev C BBB: problems getting i2c to work

I have a BBB rev C from elemen14. Everything is working fine, including getting sound from a external DAC board connected through I2S.
One thing I cannot get to work is I2C. I have tried every possible I2C port, at most I only get I2C controller timeouts.

I have tried without any pullup resistors, 10k, 4k7 and 5k6 resistors. The I2C devices (DAC chip @0x48 and serial EEPROM @ 0x50) never show up with i2cdetect.
The same devices just work without a hitch on my raspberry pi (no pullup needed).

Any thoughts how to fix this?
I am running the stock BBB debian, kernel now up to 3.8.13-bone62.

Thanks.

I have an I2C example running of Rev A5. Posted on the ADAFRUIT Beaglebone forum.

You can search for “HMC5883L compass, C programming”

Thanks, got I2C working by changing the pullup resistors to 2k2. It seems the BBB is a bit more picky then the Raspi Pi in that area.

I have an I2C example running of Rev A5. Posted on the ADAFRUIT Beaglebone forum.

You can search for “HMC5883L compass, C programming”

Thanks, got I2C working by changing the pullup resistors to 2k2. It seems the BBB is a bit more picky then the Raspi Pi in that area.

I don’t think that is true. Perhaps you are running the BBB I2C faster than the Rpi I2C? The speed will be setup in the DeviceTree.

Regards,
John