Glossary
Scope: the terms, collected in one place. Chapter references point at the fullest explanation.
API (native API) — ESPHome's own binary protocol between a device and its controllers: state out, commands in, optionally encrypted. Chapter 8.
Binary sensor — a component reporting one of two states: on or off, open or shut, present or absent. Chapter 5.
Board — the named development board a configuration targets; the name carries its pin map. Chapter 2.
Boot loop — a device crashing and restarting forever; the failure safe mode exists to interrupt. Chapter 7.
Captive portal — the small sign-in page a device serves on its fallback hotspot, for handing it new Wi-Fi credentials. Chapter 6.
Component — one building block of a
configuration: a top-level section like
wifi:, or one entry under a domain.
Chapter 3.
Device class — the declared meaning
of an entity (door, temperature), as
opposed to its type; what controllers use
to present it correctly. Chapter 5.
Domain — a top-level section holding
a list of individual things: sensor:,
switch:, binary_sensor:. Chapter 3.
Fallback AP — the device's own emergency hotspot, started when it cannot join the configured network. Chapter 6.
Firmware — the compiled program the chip runs; in ESPHome, one configuration compiles to exactly one firmware. Chapter 1.
Framework — the C++ library the
generated code stands on: esp-idf or
arduino on ESP32. Chapter 3.
GPIO — general-purpose input/output: the chip's pins, listenable or drivable. Chapter 2.
Host platform — ESPHome's build target that compiles firmware into an ordinary program for your computer, for testing logic without hardware. Chapters 1 and 4.
Hysteresis — two thresholds instead of one, so a control doesn't chatter at the boundary. Chapter 10.
I2C — the two-wire bus (SDA data, SCL clock) on which addressed sensors share pins. Chapters 2 and 5.
id — the name the configuration file
itself uses to refer to a thing, as
opposed to its display name. Chapter 3.
Lambda — a snippet of real C++ inside the YAML; ESPHome's escape hatch and its power tool. Chapters 1 and 5.
Logger — the component that produces the device's log, with its level. Chapter 9.
mDNS — the .local name system that
lets a device be reached as
greenhouse.local without a recorded
address. Chapters 3 and 6.
Noise protocol — the encryption framework behind the API's and OTA's encrypted connections. Chapters 7 and 8.
OTA (over-the-air update) — replacing a device's firmware over the network, after the first cable flash. Chapter 7.
Oversampling — a sensor measuring several times and averaging, for steadier numbers. Chapter 5.
Platform — two senses, kept straight
by context: the kind of a domain entry
(platform: bme280_i2c), and the build
target family (ESP32, host). Chapters 3
and 2.
PlatformIO — the build system ESPHome drives behind the scenes to compile the generated C++. Chapter 1.
Pull-up — a resistor (often the chip's own) holding a listening pin at a definite level until a switch overrules it. Chapter 2.
Reed switch — a contact closed by a nearby magnet; the classic door sensor. Chapters 2 and 5.
Relay — a small electrically operated switch; the pin whispers, the relay carries the load. Chapter 2.
Restore mode — a switch's declared behaviour after power returns. Chapter 5.
Safe mode — the minimal fallback firmware a device boots after repeated failed boots: Wi-Fi, logging, and OTA, waiting for a corrected update. Chapter 7.
secrets.yaml — the file beside a
configuration holding every value its
!secret references point at. Chapter 6.
Sensor — a component reporting a number on a schedule. Chapter 5.
Switch — a component the firmware, and through the API its owner, can turn on and off. Chapter 5.
Template — the family of components
(template sensor, switch, and kin) whose
values come from lambdas instead of
hardware; the simulator's entire cast.
Chapter 5.
Validation — ESPHome's offline check
of a configuration against every
component's schema: esphome config.
Chapter 3.
YAML — the indentation-based text format configurations are written in. Chapter 3.