• Mon 2019.06.24

    @maze1980, as you have explained the ground issue correctly, am a bit puzzled by your first sentence then, even with the ground issue knowledge.

    'Does the Pico request 500mA from the USB bus when connected to a PC? And what does it do when it's only allowed to use 100mA?'

    Electronic devices connected to a supply (the load) will pull what ever is needed to meet the load demand. If the Pico is at idle, then it will only
    draw the (32ma) as is indicated.

    For the (100ma) situation, if there are no other parts connected to the regulator downstream, then the load draw as explained above applies. If say ten LEDs attempting to draw more than the (100ma) supplied, then those and the Pico will be limited to the (100ma) available, and the LEDs will be slightly dimmer and possibly the Pico may not function at all. A reason to always focus on the supply first, then design the circuit.

    Remember this is Ohm Law: E = I * R   or   I = E / R   or   R = E / I


    For USB ports, the slightly older USB2 can supply (500ma) as is indicated, while USB3 can supply up to (900ma)



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