We still love the Pro Trinket but the bit-bang USB technique it uses doesn't work as well as it did in 2014. So while we still carry the Pro Trinket, we really recommend using the Metro Mini (ATmega328 @ 5V 16 MHz), ItsyBitsy 32u4 5V 16MHz, ItsyBitsy 32u4 @ 3.3V 8MHz or ItsyBitsy M0 @ 3V 48MHz. All have built-in USB and are comparable in price! The ItsyBitsy's especially are about the same size and have native USB and tons of pins, so they're a very close compatible.

Trinket's got a big sister in town - the Pro Trinket 5V! Pro Trinket combines everything you love about Trinket with the familiarity of the common core Arduino chip, the ATmega328. It's like an Arduino Pro Mini with more pins and USB tossed in, so delicious.

Trinket's a year old now, and while its been great to see tons of tiny projects, sometimes you just need more pins, more FLASH, and more RAM. That's why we designed Pro Trinket, with 18 GPIO, 2 extra analog inputs, 28K of flash, and 2K of RAM.

Like the Trinket, it has onboard USB bootloading support - we opted for a MicroUSB jack this time. We also added Optiboot support, so you can either program your Pro Trinket over USB or with a FTDI cable just like the Pro Mini and friends.

The Pro Trinket PCB measures only 1.5" x 0.7" x 0.2" (without headers) but packs much of the same capability as an Arduino UNO. So it's great once you've finished up a prototype on an official Arduino UNO and want to make the project smaller.

The Pro Trinket 5V uses the Atmega328P chip, which is the same core chip in the Arduino UNO/Duemilanove/Mini/etc. at the same speed and voltage. So you'll be happy to hear that not only is Pro Trinket programmable using the Arduino IDE as you already set up, but 99% of Arduino projects will work out of the box!

For tons more details, check out the Introducing Pro Trinket tutorial

Here's some things you may have to consider when adapting Arduino sketches:

Pins #2 and #7 are not available (they are exclusively for USB)

The onboard 5V regulator can provide 150mA output, not 800mA out

You cannot plug shields directly into the Pro Trinket

There is no Serial-to-USB chip onboard. This is to keep the Pro Trinket small and inexpensive, you can use any FTDI cable to connect to the FTDI port for a Serial connection. The USB connection is for uploading new code only.

The bootloader on the Pro Trinket use 4KB of FLASH so the maximum sketch size is 28,672 bytes. The bootloader does not affect RAM usage.

Here's some handy specifications:

ATmega328P onboad chip in QFN package

16MHz clock rate, 28K FLASH available

USB bootloader with a nice LED indicator looks just like a USBtinyISP so you can program it with AVRdude and/or the Arduino IDE (with a few simple config modifications).

Also has headers for an FTDI port for reprogramming

Micro-USB jack for power and/or USB uploading, you can put it in a box or tape it up and use any USB cable for when you want to reprogram.

On-board 5.0V power regulator with 150mA output capability and ultra-low dropout. Up to 16V input, reverse-polarity protection, thermal and current-limit protection.

Power with either USB or external output (such as a battery) - it'll automatically switch over

On-board green power LED and red pin #13 LED

Reset button for entering the bootloader or restarting the program.

Works with 99% of existing Arduino sketches (anything that doesn't use more than 28K, and doesn't require pins #2 and #7)

Mounting holes! Yeah!

Once headers are installed they can be fitted into 0.6" wide sockets

As of October 9th, 2015 the 5V Trinket comes with a micro-USB connector instead of a mini-USB connector!

Trinket may be small, but do not be fooled by its size! It's a tiny microcontroller board, built around the Atmel ATtiny85, a little chip with a lot of power. We wanted to design a microcontroller board that was small enough to fit into any project, and low cost enough to use without hesitation. Perfect for when you don't want to give up your expensive dev-board and you aren't willing to take apart the project you worked so hard to design. It's our lowest-cost arduino-IDE programmable board!The Attiny85 is a fun processor because despite being so small, it has 8K of flash, and 5 I/O pins, including analog inputs and PWM 'analog' outputs. We designed a USB bootloader so you can plug it into any computer and reprogram it over a USB port just like an Arduino. In fact we even made some simple modifications to the Arduino IDE so that it works like a mini-Arduino board. You can't stack a big shield on it but for many small & simple projects the Trinket will be your go-to platform.This is the 5V Trinket. There are two versions of the Trinket. One is 3V and one is 5V. Both work the same, but have different operating logic voltages. Use the 3V one to interface with sensors and devices that need 3V logic, or when you want to power it off of a LiPo battery. The 3V version should only run at 8 MHz. Use the 5V one for sensors and components that can use or require 5V logic. The 5V version can run at 8 MHz or at 16MHz by setting the software-set clock frequency.Even though you can program Trinket using the Arduino IDE, it's not a fully 100% Arduino-compatible. There are some things you trade off for such a small and low cost microcontroller!

Trinket does not have a Serial port connection for debugging so the serial port monitor will not be able to send/receive data

Some computers' USB v3 ports don't recognize the Trinket's bootloader. Simply use a USB v2 port or a USB hub in between

Here are some useful specifications!

ATtiny85 on-board, 8K of flash, 512 byte of SRAM, 512 bytes of EEPROM

Internal oscillator runs at 8MHz, but can be doubled in software for 16MHz

USB bootloader with a nice LED indicator looks just like a USBtinyISP so you can program it with AVRdude (with a simple config modification) and/or the Arduino IDE (with a few simple config modifications)

Micro-USB jack for power and/or USB uploading, you can put it in a box or tape it up and use any USB cable for when you want to reprogram.

We really worked hard on the bootloader process to make it rugged and foolproof, this board wont up and die on you in the middle of a project!

~5.25K bytes available for use (2.75K taken for the bootloader)

Available in both 3V and 5V flavors

On-board 3.3V or 5.0V power regulator with 150mA output capability and ultra-low dropout. Up to 16V input, reverse-polarity protection, thermal and current-limit protection.

Power with either USB or external output (such as a battery) - it'll automatically switch over

On-board green power LED and red pin #1 LED

Reset button for entering the bootloader or restarting the program. No need to unplug/replug the board every time you want to reset or update!

5 GPIO - 2 shared with the USB interface. The 3 independent IO pins have 1 analog input and 2 PWM output as well. The 2 shared IO pins have 2 more analog inputs and one more PWM output.

Hardware I2C / SPI capability for breakout & sensor interfacing.

Works with many basic Arduino libraries including Adafruit Neopixel!

Mounting holes! Yeah!

Really really small

For a lot more details, including a tour of the Trinket, pinout details and Arduino IDE examples, check out the Introducing Trinket tutorial

Trinket may be small, but do not be fooled by its size! It's a tiny microcontroller board, built around the Atmel ATtiny85, a little chip with a lot of power. We wanted to design a microcontroller board that was small enough to fit into any project, and low cost enough to use without hesitation. Perfect for when you don't want to give up your expensive dev-board and you aren't willing to take apart the project you worked so hard to design. It's our lowest-cost arduino-IDE programmable board!

As of May 27th, 2015 the 3.3V Trinket has been revised! The board is now even smaller - at just 27mm x 15mm - and comes with a micro-B USB connector rather than mini-BThe Attiny85 is a fun processor because despite being so small, it has 8K of flash, and 5 I/O pins, including analog inputs and PWM 'analog' outputs. We designed a USB bootloader so you can plug it into any computer and reprogram it over a USB port just like an Arduino. In fact we even made some simple modifications to the Arduino IDE so that it works like a mini-Arduino board. You can't stack a big shield on it but for many small & simple projects the Trinket will be your go-to platform.This is the 3V Trinket. There are two versions of the Trinket. One is 3V and one is 5V. Both work the same, but have different operating logic voltages. Use the 3V one to interface with sensors and devices that need 3V logic, or when you want to power it off of a LiPo battery. The 3V version should only run at 8 MHz. Use the 5V one for sensors and components that can use or require 5V logic. The 5V version can run at 8 MHz or at 16MHz by setting the software-set clock frequency.Even though you can program Trinket using the Arduino IDE, it's not a fully 100% Arduino-compatible. There are some things you trade off for such a small and low cost microcontroller!

Trinket does not have a Serial port connection for debugging so the serial port monitor will not be able to send/receive data

Some computers' USB v3 ports don't recognize the Trinket's bootloader. Simply use a USB v2 port or a USB hub in between

Here are some useful specifications!

ATtiny85 on-board, 8K of flash, 512 byte of SRAM, 512 bytes of EEPROM

Internal oscillator runs at 8MHz, but can be doubled in software for 16MHz

USB bootloader with a nice LED indicator looks just like a USBtinyISP so you can program it with AVRdude (with a simple config modification) and/or the Arduino IDE (with a few simple config modifications)

Micro-USB jack for power and/or USB uploading, you can put it in a box or tape it up and use any USB cable for when you want to reprogram.

We really worked hard on the bootloader process to make it rugged and foolproof, this board wont up and die on you in the middle of a project!

~5.25K bytes available for use (2.75K taken for the bootloader)

Available in both 3V and 5V flavors

On-board 3.3V or 5.0V power regulator with 150mA output capability and ultra-low dropout. Up to 16V input, reverse-polarity protection, thermal and current-limit protection.

Power with either USB or external output (such as a battery) - it'll automatically switch over

On-board green power LED and red pin #1 LED

Reset button for entering the bootloader or restarting the program. No need to unplug/replug the board every time you want to reset or update!

5 GPIO - 2 shared with the USB interface. The 3 independent IO pins have 1 analog input and 2 PWM output as well. The 2 shared IO pins have 2 more analog inputs and one more PWM output.

Hardware I2C / SPI capability for breakout & sensor interfacing.

Works with many basic Arduino libraries including Adafruit Neopixel!

Mounting holes! Yeah!

Really really small

For a lot more details, including a tour of the Trinket, pinout details and Arduino IDE examples, check out the Introducing Trinket tutorial