Re: [Cpia2-development] cpia2 Unexpected error: -71 using qx5view

[Anthony T. <an...@un...>]

On Fri, 06 Apr 2007 09:18:22 -0700, "Steven L. MILLER" <ste...@st...=
> wrote:
> According to the USB 2.0 spec, a device on a bus powered hub is allowed=20
> to consume 500mA after configuration, 100mA at powerup (this also=20
> includes power drawn by the hub).  I don't have a USB 1.1 spec handy,=20
> but I'm pretty sure the power stuff is the same. I think the 98 mA=20
> figure comes from the cpia2 chip, and doesn't include the lights. This=20
> leaves 400mA for the lights, which would be 2 watts at 5V. I don't know=20
> if this uses bulbs or leds, but the bright white leds can consume up to=20
> about 1 watt each. I'm guessing a small bulb would be about the same.=20
> This leaves things right at the edge.

=46rom my understanding the USB device requests more than 100mA if it needs
that, then the USB driver supplies that current if possible. If the cpia2
chip is only asking for 98mA then possibly the kernel is only allowing
100mA, then when the LED comes on it is above the allowable 100mA. I'm
not sure how to determine what the current kernel thinks it should allow
since that doesn't seem to be available by lsusb.

Cheers,
Anthony