nrf51822 usb device

Question

hello, 
 is there a way to have a usb stack/usb hid library for nrf51822?
I wonder if it is possible to use rx/tx port as D-/D+ to have usb connection... or even use an external uart to usb chip like (CP2102) and programme usb device? 
 thanks

Yoobe · Accepted Answer

Yes I saw this but I wanted a solution with usb hid class device and not uart. 
 I think there no cheap usb hid class device solution.. I am testing with a attiny85 board that use arduino with usb keyboard library.. 
 The project: making a mechanical keyboard with BLE and USB port. 
 The other solution I will try : teensy 3 board with BLE board
usb hid with the teensy and a ble extention for wireless device but this is not perfect as power consumption in wireless mode (teensy is not low power enough)