From: Lukáš G. <L....@sh...> - 2009-01-26 08:27:22
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>> It is as you expect - full 500mA can be drawn only after enumeration. >> Before enumeration it should be below 100mA. FT2232 has a support for it >> (pin PWREN#). > So I can't really pull 1A from two ports without having a device of some > sorts enumerated on the second port.... Any way to easily fake the > enumeration? USB spec. says it should (or have to) be done in this way. But in reality there is in most cases no protection (except fuse) on the USB ports that would prevent you from drawing >100mA before enumeration. That's why external HDDs powered from two USB ports work. They have also only one USB slave device, connected to one of the cables, on the second there is just power connection there. In my understanding they are voilating spec., but work. You must take care by yourself not to overload USB hub by connecting too much devices taking too much current (without enumeration). Lukas Grepl |