Okay, recently I got myself such a tablet. So here goes the trick. It has a hidded USB host inside. You’d like to enable it in case you want to pop in some internal goodies like an usb jump drive, gps, 3g whatsoever.
However, you have to enable the host. This is done in the following steps:
grab my sw-switcher module on github, use prebuilt one, or compile your own: https://github.com/nekromant/ampe-sw-switch
grab a copy of these: https://github.com/amery/sunxi-tools
Next, we need to alter chip’s config, so that we can enable the hidded host. To do so we need to create a new script.bin using sunxi-tools.
exec this on the tablet
mkdir /t mount -t vfat /dev/block/nanda /t cd /t
then, on the host via adb:
adb pull /t/script.bin bin2fex script.bin script.fex
Edit script.fex with your favourite editor, look for line
usb_host_init_state = 1
and change that to
usb_host_init_state = 0
save, exit the editor
fex2bin script.fex script.bin adb push ./script.bin /t/script.bin adb push ./script.bin /t/script0.bin
Reboot, and enable the host via
echo "host 1 1" > /sys/module/sw_switch/power
Disable at any time via
echo "host 1 0" > /sys/module/sw_switch/power
You are done. This also turns on and off VBUS voltage, so you get your powersaving here.