The Nokia N810 has an OTG or On-The-Go USB controller, it allows for the device to function is both client and host mode. By default it is is client mode so when you plug it into your computer it acts as a USB storage device. It can be put into host mode by feature running a program on the tablet that will put it into host mode or use the OTG trigger. The USB plug on the tablet has 5 pins rather than just the standers 4 USB uses. If the extra pin is grounded it will put the N810 into host mode.
The same is true for the N800, but the N800 uses a Mini USB connector. The N810 uses Micro USB
This is what I used to make my adapter- USB Extension Cable (any cable with a female USB type A connector will work)
- Micro USB cable with male connector
- Shrink tubing/Electrical Tape
Cut the two cables and separate the wires
This it is as simple as connecting the same color wires together, red to red, black to black, green to green, white to white, and finally the shield. I put each individual wire in shrink tubing and then the two wires in a larger piece of shrink tubing. I tried to ground the fifth pin to have it be a true OTG cable, but my soldering iron is too big and the connector is too small. (see the out of focus picture below). If anyone has any suggestions please let me know in the comments. So for now I am using one of the programs that can put the tablet in host mode for you.
Testing Time! The Device can power the devices, but it will drain your battery faster. I have tested it with USB flash drives, memory card readers, USB hubs, keyboards, and CD-ROM drives All worked fine with no problem (The CD drive had to be manually mounted)