The USB-C Connector That’s Actually a Dev Board
Hardly larger than its own USB-C port, the open source AngstromIO is a mini ATtiny1616 dev board built for ultra-compact projects.
Whatever you happen to be working on, there is a microcontroller development board out there that is a perfect fit for it. If you need lots of processing power, a Teensy or Raspberry Pi Pico will get the job done. If you need a huge number of GPIO pins, a specialty board like the Clintech Pico is what you need. But while all of these boards are fairly small, they can seem giant when you are trying to fit them into a tiny case to make, for instance, a wearable device.
Fortunately, there is a new option on the market designed especially for these types of use cases. The AngstromIO measures just 9.0 × 8.9 mm — that’s hardly larger than the onboard USB-C connector. This board isn’t about impressive hardware specs, but it will disappear into any creation, and the entire project is open source, so you can build your own.
AngstromIO is built around the Microchip ATtiny1616, a compact yet capable 8-bit MCU running at up to 20 MHz with 16 KB of flash memory. While that might not sound like much compared to higher-end boards, it’s more than enough for handling sensors, simple logic, and low-power embedded tasks. The chip’s extremely low power consumption — down to 200 nA in power-down mode — makes it particularly appealing for battery-powered or always-on designs.
Despite its size, the board packs in plenty of functionality. Two addressable RGB LEDs (SK6805) provide built-in visual feedback, while exposed pads give access to I2C (SDA/SCL), UART transmit, GPIO pins, and power rails. The USB-C connector supplies 5V power only, keeping the design minimal and compact, but also requiring an external programmer for firmware uploads.
Programming is handled via a UPDI interface, and the board is compatible with the Arduino IDE thanks to SpenceKonde’s megaTinyCore. This means developers can use familiar libraries like Wire for I2C and NeoPixel-style control for the onboard LEDs without diving into low-level AVR code.
To complement the tiny board, the creator also designed a dual-programmer module based on two CH340E chips. One handles UPDI programming, while the other provides serial output for debugging, allowing developers to monitor firmware behavior in real time.
AngstromIO is fully open source, with schematics, PCB layouts, and firmware available online. Start there if you’d like to build your own ultra-tiny development board.