For _me_ it seems, you reused an image of “Erik Kettenburg, Digistump LLC, digistump.com, 2012” as “digispark-schematic.png”, don’t you? (it would be nice to cite the original source as reference and for credits, don’t you think?)

* If you power the stump via USB only, the 5V for the chip MUST come from USB => ergo D3 must be a schottky (other symbol; must be the “fat one” between PwrLED and P0?) and point into reverse direction?! (I am not sure, if digistump did that black-hearted (-minded), cause it makes no real difference, but for the board fakers, they are annoyed of) – the symbol of the zeners is also wrong – but who cares 😉

* If you power the stump externally (Vin to MC78M05 to 5V Vcc) that diode MUST protect from reverse powering the computer (feeding power back, i.e. wrong way, into a power source)

* I think the 5V pin of (VIN|GND|5V) is only(!) designed as output, to power additional circuits, we plug the stump into?

BRs Klaus
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PS: still working on an idea for a second analog read input (for voltage level, not just resistor-ladder/poti, in additon to PB2/A1), but keeping the USB(!) for dia-log-ging… (so only PB5/A0 overload possible?)