Pro Micro - 3.3V/8MHz - DEV-12587 - SparkFun Electronics

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Pro Micro & Fio v3 Hookup Guide by SparkFun Electronics Datasheet

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ATMega 32U4 running at 3.3V/8MHz Supported under Arduino IDE v1.0.1 On-Board micro-USB connector for programming 4 x 10-bit ADC pins 12 x Digital I/Os

SparkFun Pro Micro - 3.3V/8MHz

Buy Pro Micro - 3.3V/8MHz - Atmega32u4 module - Botland - Robotic Shop

Pro Micro & Fio V3 Hookup Guide - SparkFun Learn

Arduino Pro Mini 328 - 3.3V/8MHz - DEV-11114 - SparkFun Electronics

The Arduino Micro has a built-in USB port that makes the Micro recognizable as a mouse or keyboard.The Micro is a microcontroller board based on the ATmega32U4 which was developed in cooperation with Adafruit. It has 20 digital input/output pins 7 of which can be used as PWM outputs and 12 as analogueue inputs a 16 MHz crystal oscillator a micro USB connection an ICSP header and a reset button.