I've been experiencing some issues with my custom ADAU1701 board. The board design is pretty much the same as in the ADAU1701 datasheet (page 51, I2C Control) except for the reset circuit and 1V8 Core volatge regulator, reset circuit consists of a single pull-up resistor (10k) and a shunt capacitor (0.1uF), while the 1V8 regulator is based around a LP2985-18 IC (VDrive pin is left floating on ADAU1701). The problem I'm facing is when I connect an USBi Control Interface (from an evaluation kit) and try to upload a design to the device, it fails with an error message: COMS FAILED. I've checked both the USBi connector interface and layout several times without finding the cause of the problem.
The I2C commands sent from the USBi device looks fine, except for the fact that ADAU1701 does not acknolowedge the the address. The rest of the circuitry seems fine, system clock is nice and clean, adc's are at 1.5V.
I'll be glad to hear any suggestions.