Adafruit Trinket 3.3V

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.