# Adafruit Pro Trinket 5V

> Compact ATmega328P-based Arduino-compatible board at 16 MHz, 5V, with 28KB flash, 18 GPIO, Micro USB, FTDI header, and mounting holes — a miniaturized UNO with battery-friendly power management.

## Quick Facts

- **Brand:** Adafruit
- **Board Type:** dev-board
- **Price:** ~$9.95
- **Product Readiness:** developer
- **CPU:** ATmega328P @ 16 MHz
- **CPU Architecture:** AVR
- **CPU Cores:** 1
- **RAM:** 2 KB
- **Flash:** 28 KB
- **Power:** 5V via Micro USB or up to 16V external
- **Operating Voltage:** 5V
- **Dimensions:** 38 × 18 mm
- **Weight:** 2.6g

## Open Source

- **Firmware:** Yes
- **Schematics:** Yes
- **PCB Layout:** Yes

## Compatible Firmware

arduino, platformio

## Use Cases

- prototyping
- maker
- embedded-development
- wearable

## Components

- **ATmega328P** (mcu): 8-bit AVR RISC microcontroller at 16 MHz in QFN package, 32KB flash, 2KB SRAM — same chip as Arduino UNO — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fww1.microchip.com%2Fdownloads%2Fen%2FDeviceDoc%2FAtmel-7810-Automotive-Microcontrollers-ATmega328P_Datasheet.pdf&ref=openhardware.directory&product=adafruit-pro-trinket-5v&source=md-export)

## Protocols

- **UART**: TX: D1, RX: D0
- **SPI**: MOSI: D11, MISO: D12, SCK: D13, SS: D10
- **I2C**: SDA: A4, SCL: A5
- **USB**

## GPIO Map

| Pin | Name | Type | Functions |
|-----|------|------|-----------|
| D0 | UART RX | UART | digital-input, digital-output |
| D1 | UART TX | UART | digital-input, digital-output |
| D2 | Reserved for USB bit-bang | — | digital-input, digital-output |
| D3 | Digital I/O, PWM, External Interrupt | — | digital-input, digital-output, pwm, interrupt |
| D4 | Digital I/O | — | digital-input, digital-output |
| D5 | Digital I/O, PWM | — | digital-input, digital-output, pwm |
| D6 | Digital I/O, PWM | — | digital-input, digital-output, pwm |
| D7 | Reserved for USB bit-bang | — | digital-input, digital-output |
| D8 | Digital I/O | — | digital-input, digital-output |
| D9 | Digital I/O, PWM | — | digital-input, digital-output, pwm |
| D10 | SPI SS, PWM | SPI | digital-input, digital-output, pwm |
| D11 | SPI MOSI, PWM | SPI | digital-input, digital-output, pwm |
| D12 | SPI MISO | SPI | digital-input, digital-output |
| D13 | SPI SCK, Onboard LED | SPI | digital-input, digital-output |
| A0 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output |
| A1 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output |
| A2 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output |
| A3 | Analog Input / Digital I/O | — | analog-input, digital-input, digital-output |
| A4 | I2C SDA, Analog Input | I2C | analog-input, digital-input, digital-output |
| A5 | I2C SCL, Analog Input | I2C | analog-input, digital-input, digital-output |
| A6 | Analog Input only | — | analog-input |
| A7 | Analog Input only | — | analog-input |
| A8 | Analog Input only | — | analog-input |

## Available Software

- **[Arduino IDE]()** (open-source)
- **[PlatformIO]()** (open-source)

## Description

## Overview

The Adafruit Pro Trinket 5V is a compact Arduino-compatible development board based on the ATmega328P QFN microcontroller running at 16 MHz at 5V. Measuring just 38 × 18 mm, it bridges the gap between the minimal Trinket (ATtiny85) and the full-sized Arduino UNO, offering most of the UNO's capabilities in a significantly smaller and lighter package (2.6g).

With 28KB of user-available flash (the bootloader occupies 4KB of the full 32KB), 2KB of SRAM, and 18 GPIO pins including analog inputs, the Pro Trinket can run virtually any Arduino sketch designed for the UNO. The FTDI header enables wired serial connection for debugging, and the Micro USB port provides both power and bootloader-based programming.

Power management is comprehensive for a compact board: a 150mA 5V regulator, reverse-polarity protection, thermal and current-limit protection, and support for input voltages up to 16V. Mounting holes at the four corners facilitate secure installation in enclosures or on panels.

Two pins (#2 and #7) are reserved for USB functionality, leaving 18 usable GPIO. The board does not accept standard Arduino shields due to its compact form factor but is well suited for projects requiring UNO-class capabilities in a small, mountable footprint.

## Where to Buy

- [Adafruit](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F2000&ref=openhardware.directory&product=adafruit-pro-trinket-5v&source=md-export) — 9.95

## Resources

- [product](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F2000&ref=openhardware.directory&product=adafruit-pro-trinket-5v&source=md-export)
- [wiki](https://openhardware.directory/r?to=https%3A%2F%2Flearn.adafruit.com%2Fintroducing-pro-trinket&ref=openhardware.directory&product=adafruit-pro-trinket-5v&source=md-export)

## Tags

`atmega328p`, `5v`, `arduino-compatible`, `compact`, `adafruit`, `pro-trinket`

## Images

![Adafruit Pro Trinket 5V](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-pro-trinket-5v/26afbf548b41.jpg)
![Adafruit Pro Trinket 5V](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-pro-trinket-5v/45654dfc9d32.jpg)

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