you'll just ahve 50 ohms in parallel with your real load, increasing the current drawn by another 50mA. USB devices are allowed by the spec to draw 100mA from the bus when they are initially connected. Once the device is enumerated, it can then request the host to increase this to 500mA. IF your device draws more than 500mA, you will need to power the device from multiple USB ports or to power the device from an external plug pack (e.g. some external USB hard drives do this). The USB standards and FAQs  are all available on line from (free)
Garry Allen
On 29/01/2011, at 2:33 AM, William Pretty Security Inc wrote:

Just a thought here:
If we hook a 100 ohm resistor to ground on the 5V supply pin of the USB In connector, then the Kernel will
think that a 50mA device is hooked to the port and be “fat, dumb and happy”. No ?
It will think that your 1 watt Bluetooth or WiFi dongle is only drawing 50mA, but who cares ??
From: William Pretty Security Inc [] 
Sent: Friday, January 28, 2011 9:58 AM
To: 'General mailing list for gumstix users.'
Subject: [Gumstix-users] USB Port Current limit in Kernel
Hi All;
According to Tom Calef, and others :
“If the power descriptor says that its max power > 100mA then the kernel will yell at you
saying that its above the recommended amount.
I've been trying to figure out where to shut this check off, but with no avail.
See: “External power for USB” thread
Does anybody know a way around this ??
Is there another list I could post this question on ??
"People sleep peaceably in their beds at night only because rough men
stand ready to do violence on their behalf." - George Orwell

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