I have code flashed on a SAMD20 on a Xplained Pro, and all it does is set some GPIOs and go to sleep. I power the board with a USB cable, and I see 1.8uA on the current measurement header.
I also have a PCB with a battery input and 3.3V regulator. I jumper some wires on the Xplained Pro headers to my PCB, the GPIOs disable all the hardware on the PCB and I measure 1.5uA out of the battery. At this time I can also still see the 1.8uA on the Xplained Pro current measurement header.
Now I want to power the Xplained Pro board with the 3.3V regulator on the PCB; in other words, power everything with the battery and measure the current out of the battery, expecting to see ~ 1.5uA+1.8uA
I did that by connecting 3.3V to one of the Xplained Pro pins named "Vcc". But I'm getting 6mA out of the battery, and >99% of it is going to the Xplained Pro board.
Is it possible to do this test? I've thought of possible reasons why I get 6mA:
1. debugger or USB components are getting power
2. IO leakage; but the CPU is asleep so doesn't make sense