Powering via USB breakout board: what to do with Data pins?

I'm working on a project using a Nano inside an enclosure. Power comes in via an external USB power supply connected to a USB breakout board, like this SparkFun USB Mini-B Breakout. Within the enclosure I'll run VCC and GND wires from the breakout to a (male) USB connector, in turn plugged into the Nano's USB socket.

I'm happy not having the ability to reprogram the Nano without opening the enclosure, and in fact would like to be able to power it from a laptop without it detecting the device and trying to install drivers. So I'm not planning on running a "mini USB cable" within the enclosure -- I'm not carrying D+, D- or ID to the Nano.

My question is, what should I do with the D+/D-/ID pins on the USB breakout board?

  • Nothing, let them float? It won't look like a USB device is in the box anyway.
  • Connect them to ground?
  • Other?

thanks, Mark

Terminate as standard, 120 ohm between D+ and D-, no other connection?

Thanks! So D+ & D- joined with a 120 ohm resistor, ID not connected?

        USB Breakout
        +--------+
        |    *VCC------... VCC on Nano USB ...
        |        |
        +==  *D-------+
-----++ | |      |    | 120R
USB->|| | |  *D+------+
-----++ | |      |
        +==  *ID | (N/C)
        |        |
        |    *GND------... GND on Nano USB ...
        +--------+

Do I need the same thing at the socket end (which plugs into the Nano)? Resistor between D+/-? Or just VCC & GND from the breakout? Do you have a link to "the standard"?

I think perhaps joining D+ & D- with a resistor is more to do with using USB as a battery charger?