Arduino enthusiasts searching for an alternative to the Arduino Uno with an equivalent and compatible board design may be interested in the Adafruit Metro 328 development board, which offers a ATmega328 microcontroller with Optiboot (UNO) Bootloader.
The Metro 328 has been created to provide extra features on top of what you would expect from the Arduino Uno offering plenty of GPIO, Analog inputs, hardware UART SPI and I2C, timers and PWM. The Metro 328 board is now available with headers already in place for $19.50 directly from the online Adafruit store. Features of the Adafruit Metro include the ability to power the Metro with 7-9V polarity protected DC or the micro USB connector to any 5V USB source.
The Metro board is also equipped with 19 GPIO pins, 6 of which are Analog and 2 of which are reserved for the USB-serial converter. There’s also 6 PWMs available on 3 timers offering 1 x 16-bit and 2 x 8-bit. Together with a hardware SPI port, hardware I2C port and hardware UART to USB.
On the front edge of the PCB for indicator LEDs have been installed to provide a method of easy debugging : One green power LED, 2 x RX/TX LEDs for the UART, and a red LED connected to pin PB5. The Metro 328 also comes pre-loaded with the Optiboot bootloader, which is supported by avrdude and only uses 512 bytes. For more information and full specifications jump over to the Adafruit online store by following the link below.