Adafruit QT Py - SAMD21 Dev Board with STEMMA QT

Jargon buster

Plain-language definitions for the technical terms used above.

ADC

An analogue-to-digital converter reads a changing voltage and turns it into a number the microcontroller can use. It matters when connecting analogue sensors such as light, sound, or variable-resistor sensors.

BLE

BLE stands for Bluetooth Low Energy, a Bluetooth mode designed for low power use and broad compatibility with modern phones and computers. It connects well to battery-powered and mobile devices, including Apple hardware, though it behaves differently from Bluetooth Classic and its serial-style profiles.

Bootloader

Small starter software on a microcontroller that lets new code be uploaded before the main program runs. Knowing how to enter bootloader mode matters when you need to program the board or recover it after a faulty sketch.

CircuitPython

A beginner-friendly version of Python designed to run directly on microcontroller boards. If a product supports CircuitPython, you can often program it by copying code files onto the board rather than setting up a more complex toolchain.

DAC

A digital-to-analogue converter turns numbers from the microcontroller into a real analogue voltage. It matters if you want to generate simple waveforms, audio-style signals, or variable control voltages rather than just on/off outputs.

GPIO

General-purpose input/output pins are microcontroller pins you can set in software to read signals, switch devices on and off, or connect to peripherals. The number of GPIO pins matters because it limits how many buttons, LEDs, sensors, and other parts you can wire directly to the board.

HID

Human Interface Device is a USB device class used for keyboards, mice, gamepads and similar controls. If a board supports HID over USB, it can act like an input device to a computer without needing a custom driver.

I2C

I2C is a two-wire communication bus used by many sensors and small modules. It matters because several I2C devices can share the same two wires, but each device needs a compatible address and your controller must support I2C.

I2S

I2S is a digital audio interface used to send sound data between chips, such as from a microcontroller to an audio amplifier or DAC. It matters if your project needs cleaner digital audio output than a basic buzzer or PWM signal can provide.

LED

A light-emitting diode (LED) is a small electronic component that emits light when current flows through it in the correct direction. Because it only conducts one way, its polarity matters, and a through-hole LED must be soldered the correct way around to light up.

MIDI

MIDI is a standard way for electronic instruments, controllers, and software to send musical control messages such as notes, velocity, and timing. If a board supports MIDI, it can be triggered from keyboards, drum pads, sequencers, or other music gear rather than only from buttons or code.

native USB

Native USB means the microcontroller itself handles USB communication, rather than using a separate USB-to-serial chip. This matters for programming, debugging, and projects that need the board to act directly as a USB device.

NeoPixel

A type of addressable LED system where colour data is sent along a single digital data line from one LED or controller to the next. Compatibility matters because the timing and signal format must match for the lights or driver board to respond correctly.

PCB

A printed circuit board (PCB) is a board, usually rigid, with etched copper tracks that connect electronic components together without loose wiring. Components are mounted on the board and signals route between them through the copper layout.

PWM

Pulse Width Modulation is a way for a digital pin to simulate variable output power by switching on and off very quickly. It matters for controlling things like LED brightness, motor speed, or servo-style signals from a microcontroller pin.

Qwiic

Qwiic is a plug-in connector system for I2C devices that uses small 4-pin cables, so you can connect compatible sensors without soldering. It matters because your controller or adapter also needs Qwiic, or you will need a cable or breakout to wire it up.

RAM

RAM (random-access memory) is fast, temporary memory a device uses for working data while it is running; in its common volatile form, its contents are lost when power is removed. Some devices offer a mode that applies settings to RAM only, which is handy for testing changes temporarily because they are not stored permanently and disappear at power-off.

RGB

Short for red, green and blue, the three primary colours of light that are mixed in varying amounts to make a wide range of colours. In electronics RGB can refer to an LED or pixel that blends these three colours, or to a colour signal or interface that carries separate red, green and blue channels.

RISC-V

RISC-V is an open, royalty-free processor instruction-set architecture used in chips ranging from tiny microcontrollers to Linux-capable application processors. The choice of RISC-V determines which compilers, software tools, and performance or low-power features are available, separate from the more common Arm or x86 architectures.

SAMD21

The SAMD21 is a Microchip (formerly Atmel) 32-bit Arm Cortex-M0+ microcontroller used in many Arduino-compatible boards. The exact chip affects which libraries, clock speeds and peripheral features are available, so software needs to support the SAMD21 specifically.

SPI

A fast serial communication bus often used for displays, memory cards, and sensors. It matters because SPI devices need specific pins for clock and data, plus a separate chip-select line for each device.

STEMMA

A plug-and-cable connection system used on some maker electronics boards to make wiring simpler. If a product uses STEMMA, you need the matching cable or connector type to plug it in without soldering.

STEMMA QT

A small plug-in connector system for I2C boards that lets you connect compatible sensors and controllers without soldering. It matters because it can make wiring faster and less error-prone, especially when adding several small modules to a project.

UART

UART is a simple asynchronous serial interface that sends data over separate transmit and receive wires, usually labelled TX and RX, with both ends set to the same baud rate. It is a common way for microcontrollers and other serial devices to exchange data.

USB-C

USB-C is a small, reversible USB connector that can carry power, data and, on some devices, video over a single cable. The same connector can range from charging only to high-speed data, so the functions a given port actually supports vary.