This is NOT the product I was expecting. The functionality is probably the same, but the circuitry is very different, and it seems ridiculous that a microcontroller could be used in this application. Especially when you see how they detect the voltage thresholds.
I get the impression from the ludicrous 100Mohm resistor that the circuit is just using a simple threshold system where an internal weak pull-up is used on a digital input so that a test voltage of two distinct thresholds will be detected for continuity and high voltage.
It's quite odd that one LED goes to positive and one to negative. But there are lots of oddities about the design, which could easily have been implemented on a single sided PCB.
Quiescent current is spectacularly low, so the cell stack should last a reasonable amount of time.
Although the standby current of 7uA drops to near zero after about 9 seconds when the chip goes to sleep, it was notable that a noisy electrical load in the vicinity kept it awake and drawing about 20uA.
The microcontroller seems to waken and check the inputs briefly in standby, as tapping the end of the driver is not initially detected until it coincides with a wake-up and the microcontroller goes into sense mode.
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