📊 ADC Reading

Why it matters

Sensors are analog. The ADC is how your ESP32 reads knobs, light, temperature, battery voltage, and more.

The idea

The core idea

An ADC converts a voltage into an integer code. More bits → smaller steps, but noise can still dominate.

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Demo

Gray is the underlying analog signal. Orange is the quantized ADC result. Green is a moving-average filter.

Reduce bits to see bigger steps. Increase noise to see jitter. Increase averaging to smooth jitter. Change attenuation to change full-scale range (Vfs).

Key takeaways

• Quantization turns continuous voltage into discrete codes
• Noise can dominate; averaging reduces noise at the cost of responsiveness
• On ESP32: prefer ADC1 when using Wi‑Fi
• Attenuation changes measurable voltage range (Vfs)

Going deeper

Real ESP32 ADC readings can be non-linear, especially at high attenuation. For better results: use calibration (if available), limit input impedance, and average multiple samples. For battery sensing, use a divider and keep max voltage below 3.3V (and within chosen attenuation range).

Math details

Let Vfs be full-scale voltage and N be bits:
  levels = 2^N - 1
  code = round( (V / Vfs) * levels )
  V_quantized = (code / levels) * Vfs

Quantization error (ideal) is about ±0.5 LSB.

Implementation

LLM Prompt: ADC Reading