Adafruit METRO Mini 328 has USB-to-serial built-in and is used for smaller projects. The METRO Mini 328 is a tiny, breadboard-friendly development board that is easy to use and hacker-friendly. Metro Mini can be programmed with the Arduino IDE.
The Metro Mini comes as a fully assembled and tested board, with bootloader burned in and also a stick of 0.1" header. Some light soldering is required if you'd like to plug it into a breadboard, or you can solder wires or header directly to the breakout pads. Once headers are installed they can be fitted into 0.6" wide sockets.
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