# Adafruit Trinket 3.3V

> Tiny 27×15mm Arduino-compatible microcontroller board with ATtiny85 at 8 MHz, 3.3V logic, 8KB flash, 3 GPIO pins, and Micro USB programming for minimal space-constrained projects.

## Quick Facts

- **Brand:** Adafruit
- **Board Type:** dev-board
- **Price:** ~$6.95
- **Product Readiness:** developer
- **CPU:** ATtiny85 @ 8 MHz
- **CPU Architecture:** AVR
- **CPU Cores:** 1
- **RAM:** 512 bytes
- **Flash:** 8 KB
- **Power:** 3.3V via Micro USB or up to 16V external
- **Operating Voltage:** 3.3V
- **Dimensions:** 27 × 15 mm
- **Weight:** 1.85g

## Open Source

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

## Compatible Firmware

arduino

## Use Cases

- maker
- wearable
- led-projects
- prototyping
- embedded-development

## Components

- **ATtiny85** (mcu): 8-bit AVR microcontroller at 8 MHz with 8KB flash, 512B SRAM, 512B EEPROM and 5 I/O pins — [Datasheet](https://openhardware.directory/r?to=https%3A%2F%2Fww1.microchip.com%2Fdownloads%2Fen%2FDeviceDoc%2FATtiny25-45-85-Datasheet-DS40002187A.pdf&ref=openhardware.directory&product=adafruit-trinket-3v&source=md-export)

## Protocols

- **I2C**: SDA: D0, SCL: D2
- **SPI**
- **USB**

## GPIO Map

| Pin | Name | Type | Functions |
|-----|------|------|-----------|
| D0 | I2C SDA (ATtiny85 PB0), PWM, Analog Input | I2C | digital-input, digital-output, pwm, analog-input |
| D1 | Digital I/O (ATtiny85 PB1), PWM, Onboard LED (#1 red) | — | digital-input, digital-output, pwm |
| D2 | I2C SCL (ATtiny85 PB2), Analog Input | I2C | digital-input, digital-output, analog-input |
| D3 | USB Data- bit-bang (ATtiny85 PB3), Analog Input | — | digital-input, digital-output, analog-input |
| D4 | USB Data+ bit-bang (ATtiny85 PB4), Analog Input | — | digital-input, digital-output, analog-input |

## Available Software

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

## Description

## Overview

The Adafruit Trinket 3.3V is an ultra-compact Arduino-compatible microcontroller board built around the Atmel ATtiny85, measuring just 27 × 15 mm and weighing 1.85 grams. Operating at 3.3V with an 8 MHz internal oscillator, it targets applications where size and cost are the primary constraints while still providing programmability through the familiar Arduino IDE.

The ATtiny85 provides 8KB of flash (with approximately 5.25KB available after the bootloader), 512 bytes of SRAM, and 512 bytes of EEPROM. Five I/O pins total are available — two are shared with the USB bit-bang implementation, leaving three independent GPIO pins that each support PWM, analog input, and digital I/O. Hardware I2C and SPI are supported.

Power management is robust for a board of this size: an ultra-low dropout 3.3V regulator accepts up to 16V input and provides 150mA output with reverse-polarity, thermal, and current-limit protection. The board automatically switches between USB and external power sources. A green power LED and a red pin #1 LED indicate operating status.

The Trinket uses a USB bootloader activated via a reset button, enabling programming without a separate programmer. Adafruit notes compatibility limitations with modern computers due to the bit-bang USB approach and recommends the Trinket M0 for new designs requiring reliable USB programming.

## Where to Buy

- [Adafruit](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F1500&ref=openhardware.directory&product=adafruit-trinket-3v&source=md-export) — 6.95

## Resources

- [product](https://openhardware.directory/r?to=https%3A%2F%2Fwww.adafruit.com%2Fproduct%2F1500&ref=openhardware.directory&product=adafruit-trinket-3v&source=md-export)
- [wiki](https://openhardware.directory/r?to=https%3A%2F%2Flearn.adafruit.com%2Fintroducing-trinket&ref=openhardware.directory&product=adafruit-trinket-3v&source=md-export)

## Tags

`attiny85`, `tiny`, `3.3v`, `arduino-compatible`, `minimal`, `adafruit`, `trinket`

## Images

![Adafruit Trinket 3.3V](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-trinket-3v/5635af458b53.jpg)
![Adafruit Trinket 3.3V](https://nbg1.your-objectstorage.com/openhardware-directory/entities/adafruit-trinket-3v/f2ad4d031a83.jpg)

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