Glossary

A

ADC (Analog-to-Digital Converter)

Converts analog voltage signals to digital values. The ESP32 has two 12-bit ADCs for battery monitoring and other analog inputs.

AM (Amplitude Modulation)

Radio modulation where the amplitude of the carrier wave varies with the signal. Aegis-Beacon’s CW signal is detectable by AM receivers.

Antenna

Device for transmitting/receiving radio waves. The Aegis-Beacon uses a quarter-wave wire antenna (17.3cm for 433 MHz).

Arduino

Open-source electronics platform based on easy-to-use hardware and software. Aegis-Beacon uses the Arduino framework on ESP32.

B

BOM (Bill of Materials)

Complete list of components needed to build a project. Aegis-Beacon BOM totals ~$23-28 USD.

BUSY Pin

SX1262 status pin that indicates when the radio is processing. Mandatory connection to GPIO 21.

Bootloader

Small program that runs at startup to load the main firmware. ESP32 bootloader handles USB-to-serial conversion.

C

Captive Portal

Web page that automatically opens when connecting to a WiFi network. Aegis-Beacon uses this for configuration access.

CW (Continuous Wave)

Unmodulated radio wave used for Morse code transmission. Also called “carrier” when on/off keyed.

CS (Chip Select)

SPI signal that activates a specific device. Active LOW — pulled low to select the device.

D

DAC (Digital-to-Analog Converter)

Converts digital values to analog voltage. ESP32 has two 8-bit DACs. GPIO 25 (DAC1) is used for audio output.

DDM (Degrees Decimal Minutes)

Coordinate format used in GPS transmissions. N4553 = 45 53’ N.

Deep Sleep

Low-power mode where most ESP32 peripherals are shut down. Current consumption: ~10uA. Wakes via RTC timer.

DIO1

SX1262 interrupt pin for TX/RX done and timeout events. Connected to GPIO 2.

E

E22-400M30S

Ebyte LoRa module based on SX1262. Includes onboard PA for +30 dBm output and SMA connector.

EEPROM

Electrically Erasable Programmable Read-Only Memory. Used for persistent storage. Aegis-Beacon uses NVS instead.

F

FSK (Frequency Shift Keying)

Digital modulation where frequency shifts between two values. SX1262 supports FSK for data transmission.

Firmware

Software programmed into the ESP32’s flash memory. Controls all hardware peripherals and operating modes.

Fix (GPS)

Successful determination of geographic coordinates. Requires signals from at least 3 satellites.

G

GPIO (General Purpose Input/Output)

Programmable pins on the ESP32 for digital I/O. 30 pins available on DevKit V1 (some input-only).

GMRS (General Mobile Radio Service)

US radio service for short-distance communication. Requires FCC license. Frequencies: 462/467 MHz.

GPS (Global Positioning System)

Satellite-based navigation system. Aegis-Beacon uses NEO-6M module for coordinate acquisition.

H

HDOP (Horizontal Dilution of Precision)

Measure of GPS accuracy. Lower values indicate better accuracy. HDOP < 2 is considered good.

HTML (HyperText Markup Language)

Standard markup language for web pages. Used in CONFIG portal dashboard.

I

I2C (Inter-Integrated Circuit)

Two-wire serial communication protocol. Not used in Aegis-Beacon (OLED uses SPI instead).

ISM (Industrial, Scientific, Medical)

Radio bands designated for unlicensed use. 433 MHz is an ISM band available worldwide.

J

JSON (JavaScript Object Notation)

Lightweight data interchange format. Used in CONFIG portal for settings serialization.

L

LEDC (LED Control)

ESP32 hardware for generating PWM signals. Used for precise Morse audio tone generation.

LiFePO4

Lithium Iron Phosphate battery chemistry. Better cold weather performance than standard Li-ion.

LoRa (Long Range)

Spread spectrum radio modulation technology. Provides long-range communication with low power.

M

MCU (Microcontroller Unit)

Integrated circuit containing a processor, memory, and I/O. ESP32 DevKit V1 uses dual-core 240 MHz MCU.

Morse Code

Communication method using short and long signals (dots and dashes). Aegis-Beacon uses PARIS standard timing.

N

NSS (Negative Slave Select)

SX1262 chip select pin. Active LOW — pulled low to communicate with the radio.

NVS (Non-Volatile Storage)

ESP32 flash storage that persists across power cycles. Stores configuration settings.

O

OLED (Organic Light-Emitting Diode)

Display technology with self-emitting pixels. SSD1309 2.42” provides 128x64 resolution.

OOK (On-Off Keying)

Simple modulation where carrier is turned on/off. CW mode is similar to OOK.

P

PARIS Standard

Morse timing calibration where “PARIS” = exactly 50 units. Ensures consistent WPM measurement.

PA (Power Amplifier)

Circuit that boosts radio signal power. E22 module includes onboard PA for +30 dBm output.

PlatformIO

Professional collaborative platform for IoT development. Recommended build system for Aegis-Beacon.

PMR446

European private mobile radio service. 433 MHz band, 500mW max, no license required.

R

RadioLib

Arduino library for controlling radio modules. Supports SX1262 for Aegis-Beacon.

RTC (Real-Time Clock)

Hardware clock that keeps time even when ESP32 is in deep sleep. Used for GPS fix timestamps.

RSSI (Received Signal Strength Indicator)

Measure of received radio signal power. Used in SEARCH mode to detect beacon signals.

S

SAR (Search and Rescue)

Operations to locate and assist people in distress. Aegis-Beacon is designed for mountain SAR.

SMA (SubMiniature version A)

Coaxial RF connector type. E22 module includes SMA for antenna connection.

SPI (Serial Peripheral Interface)

High-speed synchronous serial communication. Used for SX1262 (VSPI) and OLED (software SPI).

SX1262

Semtech LoRa transceiver IC. Provides CW and FSK modulation for emergency beacon.

T

TCXO (Temperature Compensated Crystal Oscillator)

Precision frequency reference that compensates for temperature changes. E22 module includes TCXO.

TP4056

Linear lithium-ion battery charger IC. Handles USB-C charging with DW01A protection.

U

U8g2

Monochrome display library for Arduino. Supports SSD1309 with full-frame buffer.

UART (Universal Asynchronous Receiver/Transmitter)

Serial communication interface. UART2 (GPIO 22/12) used for NEO-6M GPS.

USB-C

Universal serial bus connector type. Used for programming and charging.

V

VBAT

Battery voltage. Measured via voltage divider on GPIO 36. Range: 3.0V (empty) to 4.2V (full).

VSPI

ESP32’s primary SPI bus. Used exclusively for SX1262 radio communication.

W

WDT (Watchdog Timer)

Hardware timer that resets the ESP32 if firmware hangs. 30-second timeout in Aegis-Beacon.

WiFi AP (Access Point)

Wireless network created by ESP32 for configuration access. SSID: AegisBeacon, IP: 192.168.4.1.

WPM (Words Per Minute)

Morse code speed measurement. Default: 13 WPM. Adjustable from 5-40 WPM.