Adafruit Pro Trinket - 3V 12MHz

Deprecation Warning: The Pro Trinket bit-bang USB technique it uses doesn't work as well as it did in 2014, many modern computers won't work well. While still carried for maintaining older projects, it is no longer recommended. Alternatives include the Metro Mini (ATmega328 @ 5V 16 MHz), ItsyBitsy 32u4 5V 16MHz, ItsyBitsy 32u4 @ 3.3V 8MHz, and ItsyBitsy M0 @ 3V 48MHz.

The Pro Trinket 3V combines everything you love about Trinket with the familiarity of the core Arduino chip, the ATmega328. It's like an Arduino Pro Mini with more pins and USB tossed in. It offers 18 GPIO pins, 2 extra analog inputs, 28K of flash, and 2K of RAM.

Features include onboard USB bootloading support with a MicroUSB jack, Optiboot support for programming via USB or FTDI cable, and a compact PCB measuring only 1.5" x 0.7" x 0.2" (without headers). It uses 3V logic and a 12MHz clock, ideal for lower-power, lower-voltage setups.

• ATmega328P chip in QFN package running at 3.3V logic
• 12MHz clock rate, 28K FLASH available
• USB bootloader with LED indicator, programmable with AVRdude/Arduino IDE
• FTDI port headers for reprogramming
• Micro-USB jack for power and USB uploading
• On-board 3.3V power regulator with 150mA output and protections
• Supports power from USB or external sources with automatic switching
• Green power LED and red pin #13 LED
• Reset button for bootloader entry or program restart
• Works with 99% of Arduino sketches (excluding pins #2 and #7 and max 28K code size)
• Mounting holes included

Considerations: Pins #2 and #7 are for USB and not available; no onboard Serial-to-USB chip (requires FTDI cable for Serial); bootloader uses 4KB FLASH limiting max sketch size to 28,672 bytes.

Dimensions: 38mm x 18mm x 2mm (1.5" x 0.7" x 0.08"), height with MicroUSB 4mm (0.16"), weight 2.6g.