Skip to content

Glossary

Definitions of common terms used in this documentation.

A

ADC (Analog-to-Digital Converter)
Converts analog signals (like sensor readings) to digital values. ESP32 has 12-bit ADCs.

AWS IoT Core
Amazon Web Services managed cloud service for IoT device connectivity and data processing.

B

Baud Rate
Speed of serial communication in bits per second. Common: 9600, 115200.

Binary
Number system using only 0 and 1. Used by computers for all operations.

Boot Mode
ESP32 startup mode determined by GPIO0 state. Low=programming mode, High=normal mode.

Breadboard
Prototyping board with interconnected holes for building circuits without soldering.

Brownout
Condition when voltage drops below required level, causing ESP32 to reset.

C

Client
Device or program that requests services from a server. ESP32 is MQTT client.

CoAP (Constrained Application Protocol)
Lightweight IoT protocol similar to HTTP but designed for constrained devices.

Compile
Process of converting source code to machine-readable binary for the ESP32.

COM Port
Communication port on Windows (e.g., COM3). Used for USB-to-serial connections.

Core
Processing unit. ESP32 has two Xtensa LX6 cores.

D

DAC (Digital-to-Analog Converter)
Converts digital values to analog signals. ESP32 has 8-bit DACs.

Datasheet
Technical document with detailed specifications for a component.

DC (Direct Current)
Unidirectional electrical flow. ESP32 uses 3.3V DC.

Deep Sleep
ESP32 low-power mode where most functions are disabled. Wake on timer or GPIO.

Driver
Software that enables operating system to communicate with hardware.

E

ESP32
Low-cost, low-power system on a chip microcontroller with WiFi and Bluetooth.

Endpoint
URL or address where cloud service accepts connections.

ESD (Electrostatic Discharge)
Sudden flow of electricity that can damage electronic components.

F

Flash
Non-volatile memory for storing program code and data. ESP32 typically has 4MB.

Firmware
Software programmed into hardware device. Arduino sketches are firmware.

G

GPIO (General Purpose Input/Output)
Programmable pins on ESP32 for various input/output functions.

GND (Ground)
Common reference point in electrical circuits. 0V potential.

Grafana
Open-source platform for data visualization and monitoring dashboards.

H

Hexadecimal
Base-16 number system using digits 0-9 and letters A-F. Often used for I2C addresses (e.g., 0x27).

HTTP (Hypertext Transfer Protocol)
Protocol for transmitting data on the web. Uses request/response model.

HTTPS
HTTP with TLS encryption for secure communication.

Hz (Hertz)
Unit of frequency. I2C typically runs at 100kHz or 400kHz.

I

I2C (Inter-Integrated Circuit)
Two-wire serial bus for connecting sensors and displays (SDA and SCL lines).

IDE (Integrated Development Environment)
Software for writing, compiling, and uploading code. Arduino IDE for ESP32.

InfluxDB
Time-series database optimized for storing and querying time-stamped data.

IP Address
Unique identifier for devices on a network (e.g., 192.168.1.100).

J

JSON (JavaScript Object Notation)
Lightweight data format for exchanging information between devices and servers.

Jumper Wire
Short wire used for making connections on breadboard.

K

kΩ (Kiloohm)
Unit of electrical resistance. 1000 ohms. Pull-up resistors are typically 4.7kΩ.

L

Library
Collection of pre-written code for common functions (e.g., sensor drivers).

LiPo (Lithium Polymer)
Type of rechargeable battery often used with ESP32 for portable projects.

LoRa (Long Range)
Long-range, low-power wireless protocol. Not used in this toolkit (WiFi used instead).

M

mA (Milliampere)
Unit of electrical current. ESP32 typically uses 100-250mA when active.

MAC Address
Unique hardware identifier for network devices.

MQTT (Message Queuing Telemetry Transport)
Lightweight publish-subscribe messaging protocol ideal for IoT.

Mosquitto
Open-source MQTT broker software.

Multiplexer
Device that selects between multiple inputs/outputs. TCA9548A for I2C.

N

NTP (Network Time Protocol)
Protocol for synchronizing clocks over network.

O

Ohm
Unit of electrical resistance.

OTA (Over-The-Air)
Method of updating firmware wirelessly without USB connection.

P

Payload
Actual data content of a message. In MQTT, the sensor readings are the payload.

Pinout
Diagram showing function of each pin on a device.

Pull-up Resistor
Resistor that pulls a signal line to high (3.3V) when not actively driven.

PSRAM (Pseudo-Static RAM)
Additional memory on some ESP32 modules for storing larger data.

PWM (Pulse Width Modulation)
Technique for simulating analog output using digital signals.

Q

QoS (Quality of Service)
MQTT feature controlling message delivery guarantees (0, 1, or 2).

R

RAM (Random Access Memory)
Volatile memory for program variables. ESP32 has 520KB SRAM.

Reset
Restart of ESP32. Can be triggered by button, watchdog, or software.

REST (Representational State Transfer)
Architectural style for designing networked applications using HTTP.

RSSI (Received Signal Strength Indicator)
Measure of WiFi signal strength in dBm. Closer to 0 is better.

S

SDK (Software Development Kit)
Set of tools for developing applications. ESP32 Arduino Core is the SDK here.

SDA (Serial Data)
I2C data line. Connects to GPIO21 on ESP32.

SCL (Serial Clock)
I2C clock line. Connects to GPIO22 on ESP32.

Sensor
Device that detects and responds to physical input (temperature, motion, etc.).

Serial
Communication protocol for data exchange between devices. Uses TX/RX pins.

SPI (Serial Peripheral Interface)
High-speed serial bus for displays and fast devices.

SSID (Service Set Identifier)
Name of a WiFi network.

SSL/TLS
Encryption protocols for secure network communication.

Subscribe
In MQTT, to register interest in receiving messages from a topic.

T

TCP (Transmission Control Protocol)
Reliable, connection-oriented protocol used by MQTT and HTTP.

TLS (Transport Layer Security)
Cryptographic protocol for secure communication. Successor to SSL.

Topic
In MQTT, a hierarchical string that messages are published/subscribed to.

TTL (Transistor-Transistor Logic)
Type of digital circuit. 3.3V or 5V logic levels.

U

UART (Universal Asynchronous Receiver-Transmitter)
Hardware for serial communication. Used for USB debugging.

UDP (User Datagram Protocol)
Connectionless protocol used by CoAP. Faster but less reliable than TCP.

Upload
Process of transferring compiled code from computer to ESP32.

URL (Uniform Resource Locator)
Address of a resource on the internet.

USB (Universal Serial Bus)
Standard for connecting peripherals. USB-to-serial for ESP32 programming.

V

VCC
Positive voltage supply pin (3.3V for ESP32).

Volt
Unit of electrical potential difference. ESP32 operates at 3.3V.

W

Watchdog Timer
Hardware timer that resets ESP32 if program gets stuck.

WiFi
Wireless networking technology. ESP32 has built-in WiFi support.

Wiring Diagram
Visual representation of how components are connected.

X

XTAL (Crystal Oscillator)
Provides precise clock signal for ESP32 processor.

See Also