We developed 28Pins to help people to learn how to design their own boards. The board is based on Arduino project and it's part of our online course called "Learn To Design Your Own Boards" at FEDEVEL Academy. On this website you will find all the project files such Schematic, PCB or Firmware. Feel free to use it in your own personal and commercial projects. Just follow the Attribution-ShareAlike 3.0 Unported licence. Have a fun! :)
Both RESET pins ( 16U2 and 328P ) are now driven through an open drain buffer. This means: improved RESET quality and it adds an option to debug the microcontrollers through dWire.
If you would like to connect 28Pins to a board with 3.3V pins, you can. We added an option to switch between 5V or 3.3V pin voltage. Simply, just change the JP4 jumper.
ATMEGA16U2 can now be used as an universal AVRISP MKII programmer. Once you change the firmware, you can use it to program the onboard ATMEGA328P or any other board.
Micro USB (use any mobile phone or tablet charger to power the board), User Button added, DFU Disable jumper, dWire debugger (if correct firmware is used, 16U2 can work as an dWire debugger).
There are two microcontrollers placed on the board, ATMEGA328P and ATMEGA16U2.
And more ...