ADUM3160 problems

All,

I have a ADUM3160 between a USB-B connector and a Microchip PIC32MX270 processor. This is a USB UAC stereo Audio DAC capable of 24/96 and operating in the asynchronous configuration.

In the async protocol a feedback pipe is established to make sure the device and the host remain in tune and the device does not over or under run samples. The benefit of this protocol is that you can use local low jitter oscillators that are fixed and request from the host more or less samples so the local device buffer stays full.

When the PIC32MX270 gets an IN request for the 3 byte feedback request the controller sends out the data, but it looks like zeros on the host end and now that of course eventually kills the product. I have it connected to a USB3 port via a USB-C to USB3 converter if that's of any condition.

I receive data correctly and that all looks great, but when I try and send data to the host my Total Phase USB protocol analyzer says the host is receiving zeros instead of the correct protocol response.

Is it possible the drive characteristics into the 24 ohm resistors? I will check enumeration as that must be working.

Thanks,

Gordon