[Befi] wanted to add a second stage backup disk to his ODROID embedded-board server, which typically draws ~1.5W at idle. After adding the disk, he saw power consumption increase by 2W when the new disk wasn’t spinning. He thought about using one of those USB hubs with the adorable little rocker switches for each port and replacing them with transistors, but that was going to be messy. After some poking around in the USB standard, he found that most support per-port power switching (PPPS), and set about to hack a USB hub to enable software-controlled per-port switching.
[Befi]‘s NEC hub uses a uPD720112 chip which supports PPPS according to the datasheet. After tying the configuration pin labeled GANG_B to +3.3V, the hub declared itself PPPS-compatible. Of course, the manufacturer saved a penny or two by omitting the individual switches, so [Befi] added an open-drain NMOS to each port. He is using this program to switch the port on and off and made the switching transparent with autofs. [Befi]‘s current script has the bus ID and device ID of the hub hard-coded, but he intends to update it to find them automatically. This hack saves him 10W on average, which is about €30 ($40) per year.
If your hub is under powered, you could try adding an external power supply.