The Pro Micro is similar to the Pro Mini except with an ATmega32U4 on board. The USB transceiver inside the 32U4 allows us to add USB connectivity on-board and do away with bulky external USB interface. This tiny little board does all work for Arduino tricks that you're familiar with: 4 channels of 10-bit ADC, 5 PWM pins, 12 DIOs as well as hardware serial connections Rx and Tx. Running at 16MHz and 5V, this board will remind you a lot of your other favorite for Arduino-compatible boards but this little guy can go just about anywhere. There is a voltage regulator on board so it can accept voltage up to 6V(Blue board)/ 18V(Black board). If you're supplying unregulated power to the board, be sure to connect to the "RAW" pin on not VCC. This latest revision corrects the silk error from the last version of the board so that pin 14 is correctly labeled. We've also added a PTC fuse and diode protection to the power circuit and corrected the RX and TX LED circuit. Features: ATMega 32U4 running at 5V/16MHz Supported under for Arduino IDE v1.0.1 On-Board MINI USB connector for programming 4 x 10-bit ADC pins 12 x Digital I/Os (5 are PWM capable) Rx and Tx Hardware Serial Connections Our Smallest for Arduino-Compatible Board Yet! _x000D_