It can be done with a 9v easily, I'm not sure about AA's. Use a 7805 voltage regulator to give 5v power to the hub. If you want to use AA's you will need about 6 of them, or just the one 9v.
5 would easily work, and you could get by with 4 alkalines. NiMH/Cd are lower voltage, so 4 might work OK with no voltage regulator, but I can't recommend that... it's your data on the line, but I value mine too highly for that (with storage devices; obviously for mice, keyboards, webcams, etc., I will tolerate much higher risk of unreliability.)
@mrlanrat:
it's quite impressive! my n800 doesn't give out enough power for 1 sd card reader! that's what I have a powered usb hub from the wall jack. not the best option for "on the go", but then I use only 1 keyboard or 1 flash drive, so it's not that bad.
Nah... that's what md5sums are for; the backups are what I'm trying to make while potentially having power glitch induced data loss.
I don't think it's an issue with your N800 (I believe N800 and N810 are same current capability), but rather with the card reader. Most SD readers won't work, but a few are reported to. So you should do fine with one like lanrat's, if you can find it. Although, being blessed with 2 full SDHC slots, an SD reader isn't quite the need on an N800 as on the N810.
There is a battery powered hub. It uses 4 AAA rechargable batteries, it's the Cyberpower CP-H420MP. You can find it at Radio Shack, or a few places online for around $20. I've hacked mine into a different case to use AA's. Here's the thread:
sd_proto beat me to it; I was going to mention that there's already a battery powered USB hub available. I'd love to offer it along with the rest of the stuff that I've got up (don't worry, I'm still working on some more custom products guys!), but I couldn't find any supplier who had even heard of the thing, let alone was willing to give me a half decent price on it.
One other neat option for the travel conscious (not for the budget conscious... it's not a 5$ cheap part, but it's worth it) is a Solio charger. It's a combination Solar charger and Li-ion battery back that's about the size of a small cell phone. Leave it sitting in the sun either to power your hub directly, or pull it out later (charge lasts for up to like a year or something) as an external battery pack for the USB hub.
Of course that's theoretical, but I've used it to charge my N800 before and it works brilliantly... I'll try it with a USB hub at some point to confirm that it actually will work that way as well, though I don't see why it wouldn't. (That's another product that I will be adding to the store shortly btw if you're curious).
I haven't, but what would be the problem? It should work, as long as one device is in host mode, and the other is in gadget mode, and the host-mode one has drivers for what the gadget-mode one is trying to be. (e.g. N800 plays mass-storage in gadget mode, so if PDA is in host, and handles thumb drives...)
Rob, I just wanted to say my OTG adapter (now that I found it!) is working great with my N810. I am working on a novel (trilogy actually) and keep the work in progress on usb so that I can take it anywhere. I don't want to edit the actual Word docs on the tablets, but this is handy for updating notes in a text file. I just wish microb could open MHT (compressed html) files. Firefox needs a plugin to do so...
I tried the OTG dongle on my N800 that has Diablo beta installed, but no go as is. I am assuming I need to install the drivers you mentioned; I'll try that later.
