Debugging ATMEGA328 with avrdude
The programmer you mention in your other question (the Pololu USB AVR Programmer) has a built-in USB-to-TTL adapter so you can communicate directly with the micro over UART. See: https://www.pololu.com/docs/0J36/6 



According to the aforementioned document, your programmer should enumerate as both a programmer and a virtual com port within your OS; bytes transmitted to the virtual com port of your programmer go out the line labelled "TTL TX" in the above image, and whatever comes back from the micro is received on "TTL RX". Connecting the TX and RX lines to a UART on your micro should allow you to receive and transmit data back and forth between your computer and the micro.