- 30mm x 23mm (1.2 x 0.9 inch)
- On-board Micro USB connector
- 2 rows of 11 0.1″ pins, with 2 extra 0.1″ holes
- 21 GPIO pins : 8 Analog inputs, 20 PWM, 1 Serial, 3 SPI, 3 I2C
- Three on-board LEDs (2x user programmable, 1x WiFi activity) and one button.
- STM32F411CEU6 32-bit 100MHz ARM Cortex M4 CPU
- 512kb flash, 128kb RAM
- ESP8266 WiFi (802.11 b/g/n)
- All GPIO is 5 volt tolerant (Arduino compatible)
- RTC with external oscillator
- On-board 3.3v 250mA voltage regulator, accepts voltages from 3.5v to 5v (please see notes under (pinout)[#pinout] below)
- Current draw in sleep: < 0.05mA – over 2.5 years on a 2500mAh battery
- 500mA polyfuse on board
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