USB Charge and Data Transfer
CDP requires active switching on the data pins. First you initiate high current charging with the right signal on the data pins, then you switch the data pins to the usb transceiver that's handling the data. You cannot initiate it simply by providing the right voltage and current on Vusb.

See Maxim's explanation of the usb charging standards and their single IC solution for switching of CDP standards https://www.maximintegrated.com/en/app-notes/index.mvp/id/5801