Glossary

Electronics

Term	Description
Serial Peripheral Interace (SPI)	A protocol for synchronous wired communication between devices through 4 types of logic signals (CS, SCLK, MOSI, MISO) implemented using 4 wires. Follows a master-slave architecture where the main device controls communication with other devices through using clock and chip select signals. Data flows in a circle; MOSI then MISO and so on. Data packets usually contain just raw data; no overhead necessary. Usually implemented as a hardware on the MCU, but can be done in software too. There are also often pins on the module to interface with the SPI.
Logic Signals	Electrical signals that represent binary values (0 or 1) through voltage level — e.g., in a 5V system, voltages close to 5V would represent ‘1’ and 0V would represent ‘0’.
Clock Signal	A continuous, regular oscillating signal commonly used in synchronous circuits to prevent race conditions. Applied to all storage devices, flip-flops, and latches; data transfers and operations occur on specific clock edges (rising/falling) so that all components change state simultaneously.
Circuit	Any path that electricity can flow through.
Digital Circuit	A circuit that works with 1s and 0s (binary).
Integrated Circuit (IC) / Chip	A general term for a single silicon die containing multiple circuits. May just be the core processor itself or may be more of a system-on-a-chip that integrates other components like flash memory and wifi/bluetooth radio. Usually still needs other components to function though. E.g., ESP32-C3-FN4
Microcontroller Unit (MCU)	A specific type of IC. Must contain CPU, memory, and I/O all in one chip. An MCU is an IC, but not all ICs are MCUs. E.g., ESP32-C3-FN4
Module	A PCB consisting of a chip + other components like power management and I/O (or flash memory / RF if the chip doesn’t have it yet.) E.g., ESP32-C3-MINI
Printed Circuit Board (PCB)	A board made of insulating material (e.g., fiberglass) to serve as a mounting surface for components.
Universal Asynchronous Receiver-Transmitter (UART)	A protocol for asynchronous (no clock signal) wired communication between devices through 2 types of logic signals (TX, RX) implemented using 2 wires. Follows a peer-to-peer architecture.

SPI Logic Signals

Abbreviation	Name	Description
CS	Chip Select	A signal from main device to choose which sub-device to talk to.
SCLK	Serial Clock	Clock signal from main.
MOSI	Main Out, Sub In	Serial data; main → sub.
MISO	Main In, Sub Out	Serial data; sub → main.