Features:
Compatible with Arduino， based on Seeeduino.
Onboard microcontroller: ATmega328P.
Onboard Real Time Clock chip with a supercap as a backup power source.
Serial interface with DTR for auto reset during programming when operating in standalone mode. (For programming， UartSBee must be bought separately).
MicroSD card socket.
I2C Pin header (operation voltage is selectable: 5.0V or 3.3V).
User defined switch and LED.
Bee series socket - 2*10 pin 2.0mm pitch (which will mate with - one at a time - any of the wireless modules: XBee， BluetoothBee， GPSBee or RFBee.).
Please note that The IO Ports work in 0~3.3v level only.

Specifications:
Microcontroller: ATmega328P
On-board crystal frequency: 8MHz
PCB size: 92.71mm * 60.69mm
Working voltage: 3.7-5V
Power interface: 2.0mm JST/USB
ADC input: Dedicated channel(ADC0 ~ ADC3， 10bit resolution)
Connectivity: UART， SPI
Grove ports: I2C， D7， D8
RTC accuracy: ±2ppm (0℃ to +40℃) / ±3.5ppm (-40℃ to +85℃)
DS3231 temperature sensor accuracy: ±3℃
Battery JST input voltage: 3.5-4.2V
Solar JST input voltage: 4.6-6V
UART baud rate(while programming): 115200bps