“We wanted to design a microcontroller board that was small enough to fit into any project – and low cost enough to use without hesitation,” Adafruit’s Limor Fried (aka LadyAda) explained.
“[It is] 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.”
Fried describes the Attiny85 as a “fun processor,” because despite being so small, it boasts 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,” Fried continued. “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 and simple projects the Trinket will be your go-to platform.”
There are currently two versions of the Trinket: 3V and 5V. According to LadyAda, 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, [as] the 5V can run at 8 MHz or at 16MHz by setting the software-set clock frequency,” she added.
Key specs include:
- 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 16MH.z
- USB bootloader with a nice LED indicator looks just like a USBtinyISP and can be programmed with AVRdude (with a simple config modification) and/or the Arduino IDE (with a few simple config modifications).
- Mini-USB jack for power and/or USB uploading.
- 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 for reset or update.
- 5 GPIO – two shared with the USB interface. The three independent IO pins have one analog input and two PWM output as well. The two shared IO pins have two more analog inputs and one more PWM output.
- Hardware I2C / SPI capability for breakout & sensor interfacing.
- Mounting holes.