I am trying to use the SigmaStudio software to control the ADAU1761 codec on one of our pre-production boards. Since the I2C lines run directly from connector J1 to the codec on the EVAL-ADAU1X61 board, I was hoping to connect the I2C bus of our codec directly to the EVAL-ADUSB2Z board (from the EVAL-ADAU1X61EBZ kit). However, I do not know what the acceptable voltage rail is. There is a jumper on the EVAL-ADAU1X61 board to choose 1.8V or 3.3V IOVDD but I see no way for this to be communicated back to the EVAL-ADUSB2Z.
Our board uses an IO voltage of 2.75V. The ADAU1761 lists the absolute maximum voltage of the digital input pins as IOVDD + 0.3V, in our case this would be 3.05V. The EVAL-ADUSB2Z board is using 3.3V so we will exceed this (albeit only by using a pullup). If we can force the EVAL-ADUSB2Z to use 2.75V, I think we can perform our test. I do not have a schematic of the eval board, so I do not know how to make this work.
I am puzzled how the I2C interface works with the EVAL-ADAU1X61 since I see no method of communicating the proper I2C voltage back to the EVAL-ADUSB2Z. Since the I2C digital limits are based on a percentage of the rail, I don’t see how a lower voltage will work.
Do you have any thoughts on this?