search

mkorenkov / ipad_charge

charge Apple devices under Ubuntu Linux
GNU General Public License v2.0
258 stars 72 forks source link

not enough power for longer cable #9

Closed artemtk closed 11 years ago

artemtk commented 12 years ago

I have a very unique problem. I need to charge iPad3_4G over a 10 ft cable from the ubuntu machine. ipad_charge works fine with the shorter cable but will not charge on 10 ft one. I am assuming resistance is high enough to bring current bellow needed 1.1A. Can you please advice how the code needs to be modified to increase output power on the usb port? Otherwise, I am sort of stuck.

affix commented 11 years ago

This is more a problem with the length of your cable more than anything.

USB Has its limitation and a typical USB Port only puts out 500mA of current. The cable you are using could possibly have a high resistance and cut the current over a distance before reaching the 10ft distance.

USB Power Limitations (http://www.usbcable.com/usbbasics.htm)

The USB port supplies 500 milliamps on each connection. That power level will drop depending on distance and where the closest "externally powered" hub is. If you run a cable from your computer to a hub that has no other power source, then the 500 milliamps will be divided among the ports of the hub. If the hub has its own power connection, then there should be 500 milliamps from each of the ports on the hub.

Beware: not all manufacturers strictly follow the USB guidelines. But if your device needs power and isn't getting any, then you should either plug in your hubs or add an externally powered hub to provide power for your device.

bavovna commented 11 years ago

@Affix tks.