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Note: The Pro Trinket's bit-bang USB technique is a legacy approach that may not work reliably with modern operating systems. For new projects, consider an ...

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Note: The Pro Trinket's bit-bang USB technique is a legacy approach that may not work reliably with modern operating systems. For new projects, consider an ItsyBitsy or Metro Mini board with native USB support at a comparable price.

The Adafruit Pro Trinket 5V is a compact ATmega328P-based microcontroller board that packs Arduino UNO-level capability into a 1.5" × 0.7" form factor. Running at the same 5V and 16 MHz as the UNO, it's compatible with 99% of Arduino sketches right out of the box. It's programmable via the Arduino IDE using the on-board USB bootloader or an FTDI serial connection.

Key Features

  • ATmega328P Processor – Same chip as the Arduino UNO, running at 5V and 16 MHz
  • 18 GPIO Pins – Including 2 extra analogue inputs beyond standard Trinket (pins 2 and 7 reserved for USB)
  • 28 KB Flash / 2 KB RAM – 4 KB used by bootloader, 28,672 bytes available for sketches
  • Micro-USB Connector – For power and code uploads via USBtinyISP-compatible bootloader
  • FTDI Header – Alternative serial programming and debugging via FTDI cable
  • 5V Regulator – 150 mA output, up to 16V input, with reverse-polarity and thermal protection
  • Auto Power Switching – Automatically switches between USB and external battery power
  • Power and Status LEDs – Green power LED and red LED on pin 13
  • Reset Button – Enter bootloader or restart your program
  • Mounting Holes – For secure physical installation

Limitations

  • Pins 2 and 7 are reserved for USB and unavailable for general use
  • No Serial-to-USB chip — use an FTDI cable for serial monitor access
  • Cannot plug Arduino shields directly onto the board
  • 5V regulator provides 150 mA (not the 800 mA of a full UNO)

Also Consider

  • Pro Trinket 3V – Same board running at 3.3V / 12 MHz for lower-voltage projects

Ideal For

  • Compact versions of Arduino UNO projects
  • Wearable electronics and small-form-factor builds
  • Portable and battery-powered projects
  • Prototyping before moving to a final embedded design

Package Contents

  • 1× Adafruit Pro Trinket 5V (assembled, without headers)

Resources

Jargon buster

Plain-language definitions for the technical terms used above.

ATmega328P
An 8-bit microcontroller chip used on many Arduino Uno-compatible boards. Knowing the controller uses an ATmega328P helps you understand its memory, speed, pin compatibility, and the Arduino sketches it can run.
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.
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.
Headers
Rows of metal pins used to plug a module into a breadboard or connect it with jumper wires. Pre-soldered headers make the module easier to use straight away without needing to solder the pins yourself.
IDE
Short for Integrated Development Environment, a program used to write, run and manage code. It matters because some learners prefer a traditional coding workspace instead of a guided notebook-style lesson.
LED
A light-emitting diode is a small electronic component that lights up when current flows through it in the correct direction. In this kit, LEDs create the flashing effect, so polarity and correct soldering matter for the project to work.
microcontroller
A microcontroller is a small computer on a chip that runs your program and controls connected inputs and outputs. For this product, it is the part that reads buttons and sensors, drives the display and speaker, and communicates over Bluetooth.
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.
RAM
RAM is temporary memory used while a device is running, and its contents are lost when power is removed. A “Run in RAM” mode is useful for testing settings without permanently programming the module, but it may not support every feature.
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