No worries RobbH, I used to get that all the time when it was working, this is because there is a list of devices that the tablet "officially supports" and so it shows this error even though the device works. But as of a few days ago I've had a problem where as soon as I switch to host mode before I have plugged anything in I immediately get a usb device not supported error pop up once as if there is some phantom device plugged in, then when I do plug in the usb device (ive tried loads of devices that used to work before: multiple flash drives, usb keyboards even my mobile phone) nothing happens at all, the usb device gets no power whatsoever so my tablet never realises its there. I have a feeling that for some reason or other the usb controller is unable to raise the voltage of the port to the requisite 5 volts in order to power the device because whenever I switch to host mode it always says in dmesg that there was an error in a_wait_vrise and that the vbus is too slow.