I hope that this is useful information, it might relate to the fussiness that E200s have about which USB ports they will talk to.
I have made up a custom cable to connect the 9 pin USB header on my computer's main board to the similar header on the small board that carries the computer's front USB ports. The only connections made are for Data+, Data-, Ground and +5Volts (which I have cut). A 200 mA meter is connected into the +5Volt line. 200 mA is not quite as big as what I would like, but it is what I have. The small board with the USB sockets has the +5Volt and Ground lines of the USB sockets joined together.
So, there is effectively a normal USB socket and a crippled USB socket with power and no data. The motherboard is an Asus K8V-VM. All 8 USB ports (4 back panel plus 4 from headers) are claimed to be USB 2.0.
The current drawn by my Sansa E260 is not what I expected.
When the battery is well charged and the E260 is off, plugging the USB cable in causes the Sandisk logo to be displayed and about 150 mA to be drawn. Then the small text of the RockBox bootloader is displayed and the current drawn *increases* to about 180 mA. Then, when the OF is running, the current falls to about 90 mA. The screen with back lighting and scrollwheel seem to take about 45 mA. The steady state, battery charged, screen off, not playing anything current seems to be about 42 mA. Calculating from the battery rating of 750 mAh and SanDisk's claim of 20 hours battery life gives a minimum current of 37.5 mA.
If the battery is only half charged when the cable is connected the currents drawn are even greater, sending my 200 mA multimeter off the scale during boot up.
I also tried putting a 12 Ohm resistor in the +5Volt line. That usually resulted in the E260 showing a warning message like, "Battery too low shutting down".
I assume that neither bootloader attempts to negotiate current requirements with the host and so neither bootloader (or the E200 as a whole) is compliant with USB 2.0.
Interestingly I can not find any claims by SanDisk that the E200 is USB 2.0 compliant - despite the claim that the Portal Player is USB 2.0 OTG compliant.
There is yet another opportunity for RockBox to surpass the OF. ;-)