Develop a circuit with the following functionalities.
- ATSAMD21G18 incl. adapted Arduino bootloader and documentation
- 3x RS232 connection using the MAX3232
- At least six GPIO ports
- Input voltage: 12 V
- TCXO with at least 2.5PPM
The circuit should be designed incl. PCB in Eagle and the components incl. order number should be listed at Mouser or Farnell. In addition, a prototype PCB is to be developed and built incl. example script.