AVR Input/Output expansion
==========================

Modules
-------
| Module                        | Header   | Enable Config                             | Description                                            |
|-------------------------------|----------|-------------------------------------------|--------------------------------------------------------|
| [IO Ports](modules/ioport.md) | ioport.h | CONFIG_IOPORTS and CONFIG_IOE_PCINTERRUPT | Simple input/output port access                        |
| [SPI](modules/spi.md)         | spi.h    | CONFIG_SPI                                | Serial peripheral interface                            |
| [USART](modules/usart.md)     | usart.h  | CONFIG_USART                              | Universal synchronous/asynchronous receive/transmitter |