Atmega32U4 Development Board

This is a small microcontroller development system incorporating the Atmega32U4 micro (the TQFP44 package version) used in the Arduino Leonardo, Micro, and Pro Micro (maybe others). I picked it because it comes with a USB bootloader preinstalled. Note that the bootloader is not compatible with the Arduino IDE. However, it allows the use of Microchip Studio to write embedded code that's more predictable than the Arduino IDE output. Programming is via an application called FLIP (FLexible In system Programmer), which is free. Other than that, all you need is a USB cable and your development system is complete. I picked the PCIE connector simply because it reduced the component count on the dev board and it's compact. And the 36 pin PCIE connectors aren't particularly expensive.