The Slider

The Cyber Fidget has an analog slider — a physical control you can move from one end to the other. Your app reads its position as a number and uses it to control anything: volume, brightness, speed, or selection.

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What is this?

The slider is an analog potentiometer. As you move it, the voltage on a pin changes. The ESP32's ADC (Analog-to-Digital Converter) reads that voltage and turns it into a number you can use in code.

Like a dimmer switch

Think of a light dimmer: twist it one way, lights get brighter; twist the other, they dim. The slider works the same way — it reads a position from one end to the other.

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Global variables

The HAL updates these values every loop. Use the ones that fit your needs:

Variable	Range	Use case
sliderPosition_Percentage_Filtered	0–100 (float)	Intuitive 0–100%
sliderPosition_Percentage_Inverted_Filtered	0–100 (float)	Same, but direction flipped
sliderPosition_8Bits_Filtered	0–255 (int)	Good for RGB/brightness
sliderPosition_8Bits_Inverted_Filtered	0–255 (int)	Same, inverted
sliderPosition_12Bits_Filtered	0–4095 (float)	Full ADC resolution
sliderPosition_12Bits_Inverted_Filtered	0–4095 (float)	Same, inverted

Filtered vs raw

The "Filtered" variants are smoothed to reduce jitter. Prefer these for UI and control logic. Raw values (sliderPosition_12Bits, etc.) are also available if you need unfiltered readings.

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Kalman filtering

The raw ADC readings jump around due to electrical noise. The framework applies a Kalman filter plus an Exponential Moving Average (EMA) on the percentage to smooth the signal. You get stable, responsive values without coding the math yourself.

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Code example: slider-controlled volume

#include "HAL.h"
#include "globals.h"

void update() {
    // Map slider 0–100% to volume 0.0–1.0
    float volume = sliderPosition_Percentage_Inverted_Filtered / 100.0f;
    HAL::audioManager().setVolume(volume);

    // Use 8-bit for LED brightness
    int brightness = sliderPosition_8Bits_Inverted_Filtered;
    HAL::setRgbLed(pixel_Front_Top, brightness, 0, 0, 0);
    updateStrip();

    // Display percentage on screen
    display.drawString(64, 20, "Slider: " + 
        String((int)sliderPosition_Percentage_Inverted_Filtered) + "%");
}

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Framework details

ADC reading

The slider is connected to GPIO 35 (ADC1_CH7). The ESP32's 12-bit ADC yields values 0–4095. The HAL reads this in sliderPositionRead() and updates all derived variables.

Filtering pipeline

1. Raw read — analogRead() → 0–4095
2. Kalman filter — Smooths 12-bit value
3. Derived values — 8-bit = 12-bit >> 4; percentage = (12-bit / 4095) × 100
4. EMA on percentage — Reduces jitter in the 0–100% output

Inverted variants

Some hardware builds wire the slider so "top" gives low voltage and "bottom" gives high (or vice versa). The *_Inverted_Filtered variables flip the range so 0% = one end and 100% = the other, regardless of wiring.