o 30mm x 23mm (1.2 x 0.9 inch)

o On-board Micro USB connector

o 2 rows of 11 0.1 pins, with 2 extra 0.1 holes

o 21 GPIO pins : 8 Analog inputs, 20 PWM, 1 Serial, 3 SPI, 3 I2C

o Three on-board LEDs (2x user programmable, 1x WiFi activity) and one button.

o STM32F411CEU6 32-bit 100MHz ARM Cortex M4 CPU, 512kb flash, 128kb RAM

o ESP8266 WiFi (802.11 b/g/n)

o All GPIO is 5 volt tolerant (Arduino compatible)

o RTC with external oscillator

o On-board 3.3v 250mA voltage regulator, accepts voltages from 3.5v to 5v

o Current draw in sleep: < 0.05mA - over 2.5 years on a 2500mAh battery

o 500mA polyfuse on board