The AVR P4 Field Engagement Board (FEB) offers ultimate solution for the low power application with high performance and precision of an AVR microcontroller (MCU). The device is compact in size with low pin count and small memory size.
Maximizing the value of 20 AVR pins:

2 pins for VDD and GND
1 pin for Unified Programming and Debug Interface (UDPI)
2 pins for 32768 Hz crystal oscillator
4 pins for 4 LEDs and 4 push buttons
3 pins for interface to OLED display
1 pin for SET/RUN slide switch detection
6 pins for connector and I2C bus connection

Demonstrated techniques:

How to use 1 pin for both driving a LED and detecting a push button
How to switch between oscillators on-the-fly

Use 20 MHz internal oscillator when fast processing is required for driving display
Use 32768 Hz external crystal oscillator when precise timing is needed
Use 32 kHz internal Ultra Low Power (ULP) oscillator otherwise to minimize power consumption

How to use only 3 pins to drive a 128 x 64 OLED display
How to expand each display character on-the-fly to 12 x 16 pixels so it is easy to read but only uses 6 x 8 bits of Flash
How to make a design where part of the circuit can be switched off to minimize power consumption (without accidentally resetting the MCU)

Key Features :

AVR ATtiny416 microcontroller
4 KBytes In-system programmable Flash
128 Bytes EEPROM
256 Bytes SRAM
OLED display
Piezo buzzer
4 LEDs, 4 push buttons
UPDI connector mounted to the board – program and debug using the Atmel-ICE
External power connector mounted to the board – power the board with external power
Connector board layout for external connection

Relevant Resources:
MASTERs 2017 – LAB Manual for 21110 LPD1
8-bit AVR P4 Sell Sheet
ATtiny416/816 Summary Data Sheet
ATtiny416/816 Data Sheet
Official Weblink