Hello all. I am trying to take the micro usb part of this cable and make another charger for my n900 using a ac-8u from another nokia device. Ihave the red and black off the charger but i dont want to start crossing wires on the usb cable.

Anyone know which wires provide power and ground? There are 5 total in the cable they are as follows:

White
brown
green
grey

i tried to make the grey ground and the brown 5v but it didnt charge. Any help would be appreciated