Telling them apart

Six levels, five lines

SIGNAL can sit at six levels, and a sketch has to say which. The simple way is to draw a line halfway between each pair of neighbours. A reading above a line and below the next one up is that push.

In thousandths of VCC:

The sketches carry exactly this list, highest first, and stop at the first line the reading is above:

const int LIMIT[] = {722, 359, 227, 146, 56};

One number for every board

An Uno and a Pico count from 0 to 1023 against their own supply, which is VCC, so the count over 1023 is already a fraction of VCC. An ESP32 and an ESP32-S3 count to 4095 against a reference inside the chip; there the sketch asks analogReadMilliVolts for calibrated millivolts and divides by 3300. Either way the sketch ends up with thousandths of VCC, and one list of lines fits all four.

The ESP32's ADC reads nothing below about 0.1 V and tops out near 3.1 V. Neither end matters here: up, the lowest push, is 0.37 V, and right's full 3.3 V reads as the top of the scale, far over its line at 722.

How much room there is

The closest pair is up and the press: a ninth and two elevenths of VCC, 0.071 of it apart. That is 72 counts on an Uno and 233 mV on a 3.3 V board, and the line halfway leaves half of it either side.

The resistors are 1 % parts. Worked through every combination of all six at the ends of their tolerance, no level moves by more than about half a percent of VCC: 16 mV at 3.3 V, 5 counts on an Uno. Noise on a breadboard is a few counts more. Both are small against 36 counts of room, which is why no calibration step is needed.