On Mon, 12 Mar 2007, Gordon McLellan wrote: > My phone, a Nextel i830 (motorola) draws as much as 750mA when > charging a low battery and transmitting at the same time. > > I've modified the datacable to try to charge from USB, but the > per-port current limit quickly kicks in and puts an end to it. > > As I understand it, the 500mA as per the usb 2.0 spec is only > available after a device enumerates as needing that much current. > The default of 100mA is all that will be allowed, unless the device > specifically asks for more. I don't think my phone enumerates as a > high power device, since I'm not able to draw more than 100mA. I
You don't have to guess. Look in /proc/bus/usb/devices. > don't think there's anything that can be done on the host side to > enable more current, the limits are probably imposed at the microcode > level, inside the USB host interface chip. As far as I know, the chip's only limit is 500 mA. You should be able to tell if a device is violating a current limit, though; there would be an "overcurrent change" message in the system log. > On older computers, those having only usb 1.1 ports, you might be able > to get the full 500, or more, since I don't think current-limiting > routines were imposed until 2.0 came around. Alan Stern ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Linux-usb-users@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-users
