The Teensy 2.0 from PJRC.COM (Paul J Stoffregen and Robin C Coon) is an 8bit MCU built around the ATmega32U4 processor. It includes a clock speed of 16 MHz with 32K of programmable flash, 1K of EEPROM, 2.5K of SRAM, 25 GPIO lines, 32 working registers, four timer/counters, one high-speed timer, 12 channels of 10-bit ADC, and a variety of communication protocols, including USART, I2C, SPI, JTAG, and USB. The module is programmed via a USB cable with no intervening hardware, and all development tools are freely-available online.
General Information
Getting Started #3: C Compiler (PCJR.com) For this step, Mac users can use this alternative link For MacOS "blocked App" errors see this link
Detailed References