Picoino Cell R3 Atmega328p-au Microcontroller Board, 3V, 8mhz Arduino Compatible with Coin Battery Holder and Nrf24l01+ Wireless Transceiver (Or with Small Modification Esp8266 Wifi) Module Socket Low current consumption (down to a few microamps / yA) CR2032 coin battery board with NRF2401+ wireless transceiver socket. 100% Arduino IDE compatible. You can use some of those CELL boards to build a wireless mesh network. You can also use an ESP8266 module if you modify the board. This way you can build a very small webserver, router, etc. Instructions tell you exactly how to modify the board! 3V with on board coin battery or 3-5V with external power source. ATmega328P microcontroller with Optiboot Arduino compatible bootloader.. 8Mhz Clock Speed with precise crystal oscillator, 32k Flash Memory, 14 Digital I/O Pins (6 PWM outputs) + 8 Analog Ports This board has no power regulator or other power hungry devices and the 2 LED indicators can be connected/disconnected. There is an FTDI interface connector and you can connect it to USB with an optional FTDI/USB breakout board. The CELL R3 is the perfect solution for sensors or applications where you need to run it off a small battery for years. Comes with detailed English instructions (pdf online link), mounting frame (random color), 3 pin headers and coin battery holder to be soldered. Attention: It doesn't come with the optional NRF24L01+ Module.