It lives!

The pile of parts is charging up an iPad!Basically you have the power going to the charge switch (square chip second from the right) to the USB port with the embedded sense resistor. The charge controller (all the way on the right) is letting the iPad know it's allowed to draw 2.1A. The sense resistor's voltage is going to the sense amplifier (all the way on the left). That, in turn, is going to the analog to digital converter (ADC) on top.The ADC's output goes over I2C to the micro controller (an Arduino in this case) that's monitoring the charging.That gets sent over serial to -- well -- nothing at the moment. But the scope is there monitoring it none-the-less.The ASCII is the output of the ADC in text.With the 10mΩ sense resistor and the 100 V/V amplifier the result is 1V/A at the input of the ADC. This is convenient because the unscaled value of the ADC is in mA.Above (take a minute or two after the multimeter shot) is reading 1551mA -- or 1.551A... which is pretty darn close to the multimeter output!All that's left to do is hook up the IO expander (that was blinking the LED before) and have that control the power switch and read any faults.Then... then I have to build a circuit board.  :-)  Then maybe launch a kickstarter or something.Speaking of boards -- I came to a realization today. I was planning on building a modular system before, but I think I was overthinking things. I was thinking of spinning multiple versions of the board depending on how many ports are needed. An easier way is to build a master board with an I2C mux (multiplexer) and have that just chain to sister boards. This way I can have one board and optionally populate the mux and associated circuits or not. Having one board definitely makes thing cheaper.