2 docs tagged with "calibration"

A successive-approximation ADC is, physically, a capacitor with a switch in front of it. Converting a voltage happens in two completely different phases: first the switch closes and the capacitor is allowed to charge towards your signal through the source impedance, and then the switch opens and a comparator plays twelve rounds of twenty questions against the trapped charge. The second phase is fixed by the hardware and takes exactly twelve clocks. The first phase is the one you configure, the one every tutorial leaves at its reset value, and the one that decides whether your reading means anything at all.

Every other peripheral in this folder lives in your power domain, stops when you stop, and forgets everything when the supply goes away. The RTC does not. It is a small independent machine in a separate power domain with its own oscillator, its own supply pin, and its own reset — and the only things it shares with the rest of the chip are a bus interface and a couple of locks that exist specifically to stop your code from disturbing it by accident.