Running out of USB ports on my PC and having a plethora of USB wall-wart chargers, I wanted to be able to use them.
When I plugged a mini-USB cable into them and then into my TWR-ELEV (primary) PCB, I couldn't get any power to the TWR. After a bit of research, I found that if you short together the DP and DM pins of the USB socket, the device becomes a "Dedicated Charging Port" (DCP which can be sourced up to 1.5A) and is recognized by the charger (and PCs) as such.
The DP and DM lines are Pins 2 & 3 of the socket and with a steady hand (and probably a microscope) they can be shorted together on the TWR-ELEV board (if you look at the schematic, these lines along with the identification line (ID) on Pin 4 are floating).
This is NOT recommended for any other boards but for the two TWR-ELEV primary PCBs I have, it works quite nicely and eliminates the need to plug into a PC for power.