Android phone always charges when connected by USB


I hope this is the right area of the forum for this post. My apologies if not.

I have an Android app which controls two servos via the Arduino connected by a USB shield. I power the Arduino with a 9v battery and each of the servos by a 4 x 1.5v pack.

The phone is a HTC Desire HD and under Settings → Connect to PC I have selected Disk Drive as Default Connection Type. However, as soon as I connect to the Arduino it starts charging. I’ve also tried various other options as Default connection Type, but the phone always starts charging as soon as it’s connected and sucks power out of the batteries.

Does anyone know how to prevent this?

Thanks in advance.

Which arduino ?

If its the ADK its supposed to do that. The ADK interface is very similar to the origional usb shield so i would expect the same behavior.

As im using ipad i am limited to the redpark serial lead so use serial interface not usb.

snip the powerlines and leave the data lines free?...

unless there's some kind of check to make sure there's power, it should work.?

Not sure on terminoligy but it was explained to me that the phone is a slave not host and expects to see power. Not tried it myself, so i guess snip the volts and see what happens.

Hmm. A bit more research suggests this can be done only by connecting a resistor into the USB cable and that doesn't work reliably with the HTC Desire. I guess I'll connect a supply from a wall socket instead.