Overview of Digital Signals and Pulses

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Updated October 29, 2026

In the conceptual model, an analog signal can take infinitely many values within a range, while a digital signal uses discrete levels; a binary example uses high and low. A train of digital pulses can carry information through pulse width, as in PWM, or be counted by its edges. Knowing this helps you read the articles about IO pins and communication.

Contents

An analog signal is modeled as varying continuously; a digital signal has discrete levels.

Analog signal
Digital signal

What you will learn

Tell analog signals from digital ones.
Name the high and low logic levels.
Describe PWM and pulse counting.

Before you start

No prior knowledge needed.

How do analog and digital signals differ?

In the conceptual model, an analog signal can take infinitely many values within a range. Digital signals use discrete values; a binary example uses only two levels. Most microprocessors and logic blocks process information using digital logic; real systems can still contain analog parts.

The analog model allows any value in a range; a digital signal uses a discrete set.

Analog: continuous
Digital: jumps levels
Discrete levels

What is a logic level?

A logic level is a signal state interpreted using voltage thresholds. The binary example here has two levels, HIGH and LOW in Arduino; these correspond to voltage ranges, not necessarily one exact value. Which level turns a device on depends on the circuit. Before connecting signals, check voltage compatibility between devices; a voltage that is too high can damage an input not rated to tolerate it.

Binary logic example: HIGH and LOW; real circuits interpret them using voltage thresholds.

Digital signal
High level (HIGH)
Low level (LOW)

How are pulses made and counted?

Pulse width modulation (PWM) is a digital signal that switches between HIGH and LOW. At a fixed period, changing how long the signal stays HIGH changes its duty cycle — the fraction of the whole cycle spent high, often expressed as a percentage.

The ESP32 pulse-counter peripheral (PCNT) can record incoming edges. Each counter unit has multiple channels, and each channel can increment or decrement the count on a rising or falling edge.

At a fixed period, wider pulses increase the fraction of time spent high.

Narrow pulses, low duty cycle
Wide pulses, high duty cycle
Illustrative average level

The analog model allows infinitely many values; a digital signal uses discrete levels.
The binary logic example distinguishes HIGH and LOW; real devices interpret them using voltage thresholds.
PWM changes the time spent HIGH; ESP32 PCNT records pulse edges.

Terms in this article

English and Vietnamese terms, with the meanings used here. Hover, tap or Tab to a term with a dotted underline for an explanation as you read.

Analog signalTín hiệu tương tự: In the conceptual model, an analog signal can take infinitely many values within a range.
Digital signalTín hiệu số: A signal using discrete values; a binary example has two levels.
Logic levelMức logic: A signal state interpreted using a circuit’s voltage thresholds; HIGH and LOW need not mean one exact voltage.
Pulse width modulationĐiều chế độ rộng xung: A digital signal that varies its time at the high level to give an analog-like effect.
Duty cycleChu kỳ làm việc: The fraction of one cycle for which a signal is high, often expressed as a percentage.
Pulse counterBộ đếm xung: A hardware block that counts rising or falling edges of a signal.
EdgeSườn xung: The moment a signal goes from low to high (rising edge) or high to low (falling edge).

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