I"m going to explain my problem real quick first. So there is lack of a back up solution for photographers that is cheap light and small, such as a usb or SD card copiers. I want a cheap solution and not have to drop 300-400$ for a back up solution for photos. So my thought was just use a secondary thumbdrive or SD card reader as my back up, leave the back up behind when i'm out on a shoot just in case something happens to my gear. Now I have come across http://www.amazon.com/EZ-Portable-Duplicator-Tester-EZ2USB/dp/B003N4D7BE/ref=pd_cp_e_2 which is still a bit pricey and bulky imo.
So my project/question is what would I need, and how much coding is involved in just transferring files between two usb ports, is an Arduino board capable in doing so as well? Sorry forgive my lack of knowledge about arduino's.
Requirements -
2 USB ports - one for primary and one for secondary/backup
1 button to start the transfer between the two
1 LED light for activity of the xfer
If this works down the road -
Add a second button to format the secondary/back up solution
Battery powered?
You need a USB host shield to do this. The USB port on the arduino is not a host.
Believe it or not, FTDI actually has this exact solution available in the Vinculum VN-1 chipset. They even have a demo board that does exactly what you are trying to do (VF2F2). They also have an arduino shield for their Vinculum chips. http://www.ftdichip.com/Products/Modules/DevelopmentModules.htm
An SD card copier would be much much more simple to implement on the arduino.
Sorry I should have been more specific, it would use USB and I could plug in a SD Card Reader to the USB for file transfer on either side. OR just 2 SD Cards Readers on either side