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@tage
if you are interested in measuring solar panel current you can just place the current sense resistor in series with the negative wire coming from the solar panel, because the solar panels are designed to float (up to 600V or 1000V from earth ground). solar panels usually have a ground connection, but that is connected to the metal frame. the solar cell package is floating.
you then just connect an opamp as an inverting amplifier with two resistors, to amplify the measurement signal 3.3/0.1 = 33 times, and connect the opamp output to the ADC pin. it is not necessary to place the sense resistor in the positive lead and level shift the signal when measuring solar panel current of a low voltage solar panel.
it is different if you measure on a solar panel array that is connected to a nonisolated dc/ac inverter. then you need isolation for safety reasons. Avago has some good optoisolated current amplifiers, for example ACPL-782T can withstand 3750Vrms from sensor to output.
the reason why I am using a median filter is that I want a steady reading for display on an LCD alphanumeric display or on a computer screen, and I update the display at 1Hz so I can afford the computing delays. if I was to use the current measurement for charge controller function I think I would use less filtering on the signal that is used for the controller. in my power converter I am using the output from the LT1999-10 for the current limit function, so I cannot filter the signal too heavily before applying it to the controller. but this current control function is implemented by analog circuitry (opamps).