USB host mode
Note: This is about pre-N900 devices, i.e. OS2008. The N900 does not support full OTG, but has a hostmode that's quite a bit different to that of older devices. See discussion for details, implementation of h-e-n, as well as usb on the n900
USB host mode allows you to connect various USB devices (external hard drives, digital cameras, card readers, input devices, etc.) to your device just like a regular computer. There are, however, a few limitations. The device must draw under 100mA (this can be bypassed by using a powered hub), and you will need a hardware adaptor to plug a fullsize USB cable into the tablet's undersized one.
 USB On-The-Go
The USB port on the tablets is a USB OTG, this means that they can be switched between client- (where you plug the tablet into a computer—for flashing and mounting cards on the computer), and host- (where the tablet acts like a computer) mode with the correct hardware adaptor.
You can find a USB OTG adapter designed specifically for the N800 and the N810 (N810 owners will need to buy both adaptors until a custom N810 adaptor is manufactured). These OTG adaptors will automatically switch the tablet into host-mode when plugged in.
You can also buy a "dumb" adapter that will provide the correct connections, but will not automatically switch the tablet into host-mode from most online and some in-store retailers. Then you can simply switch into host-mode manually.
 Switching modes with software
There are two options for switching between client- and host-mode in software. If you want to switch modes using a statusbar application, install the usb-otg-plugin, if you prefer to use a separate application for switching modes, then install USB Control. Both pieces of software accomplish the same thing, they just provide slightly different interfaces to do it.
 Switching modes manually
To manually switch USB modes, you must first have rootsh installed, then open xterm and type:
sudo gainroot echo host > /sys/devices/platform/musb_hdrc/mode
The tablet will then be in host-mode and you can use your USB peripherals. To set the tablet back to client mode, open xterm again and type:
echo otg > /sys/devices/platform/musb_hdrc/mode
- This page was last modified on 5 December 2010, at 20:12.
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