I designed a simple break out board for the Arduino Pro Micro.
You can order the boards for this project at https://oshpark.com/shared_projects/wye2qIl8.
The 3 pin PC fan style headers make it really easy to plug in analog and digital I/O quickly.
This board has 12 headers for A0 - A3, D4-D10, and D15. Each header has the VCC and GND on either side of the I/O pin.
The headers can be used with any standard 2.54mm/0.1" headers but the board was designed for 3 pin PC fan style headers like these https://tinyurl.com/yafg9g5g.
There are optional 0603 SMD footprints are added to the Analog and half of the digital pins. These footprints do not need to be populated, they do make it easier to wire in pulldowns and filter capacitors if you have 0603 parts to use.
The board also breaks out D0-D3 on separate I2C and UART headers.
The I2C header is positioned for a 128x64 SSD1306 OLED, like these https://tinyurl.com/y8888a49.
I will add another step showing the fully assembled board when I get the first boards in.