This is a 24-pin development board designed for the ATtiny3227. It features an integrated analog multiplexer that automatically routes signals between UPDI programming and UART serial communication. The board can be powered either via USB or through a separate external power input that accepts 6V to 12V. For maximum flexibility, all of the microcontroller's I/O pins are fully broken out into port-grouped headers.

Pin PA7 is connected to a onboard LED for quick testing purposes.

The Arduino IDE can be used for programming. Uploading your code to the board is via UPDI (selected on the board with the slide switch) and if you have any Serial.Println(); commands, the UART selections can be used to view the output on the Serial Monitor.

Power and Connector Rules:

1. J2 (External Power Input): Used to power the board after programming. CRITICAL: Do not connect power to J2 while the board is simultaneously connected to USB power.
2. J5 (Auxiliary Power Output): Provides a common ground (GND) and a regulated 5V supply for external components.
3. J5: The ground pin on J5 must be used as the common return path for all J3, J6, J7 and J8 outputs.

LED Status Indicators:

• D1: Illuminates when USB power is active.
• D2: Illuminates when external power (6V–12V) is active.
• D5: Functions as the TX status indicator, flashing during serial data transmissions from the ATtiny.

The design of the board is now on Revision V2.0 with a few technical enhancements added. The "real life" photos of the board is from the prototype V1.0 board.