arduino and Sony PSP

hello every body

I'm a french artist in residency in Japan I make a project with Sony psp and arduino. I use a digital Compass (cardinal point on 3 digital bit) link an arduino and a serail protocol between my psp and arduino. The psp generate sound in fonction of your position. Like in this noisy demonstration :) : http://atonews.blogspot.com/2007/11/cardinal-point-turntable.html

but I have a small problem : when i use the 9v battery directly on my arduino and I launch my psp application I have a bad serial datagram with many error. but if I connect the usb port (but the arduino switch is plug on extern alimentation) and I launch my psp application I found the good value by serial .And the most strange thing it's after I can unplugged the usb and my device work very well. It's like if my dispositif needed to be connected by USB to begin a good serial communication. I think that it's a ground mistake, but I have no idea.

Please help me! this is really null to need to use a big computer to launch my small system (psp+arduino).

thanks

ok sorry

i changed my 9v battery by a good toshiba (not a cheap price battery) and now it’s ok ;D

do you have an idea of the life of a 9v battery with arduino?
i have just a small digital compass RDCM 802 connected to the arduino.

Like 9 hours, depend on the number of components attach to Arduino. If you one more autonomy, you can use 6 battery of 1.5V the big one "C".

If live in japon, you can look for a radio control rechargable battery, with 8.7 volts, that will give you a lot more of time, a lot and you can recharged.

oh great

but do you have just a picture link of this kind of battery ? I don't speak a good japanish :-? so i use image to ask something in the electronic shop

I need of a small battery to glue it behind the PSP

thanks :)