Atmega328P UART Levels

This won't work with a 328p at 5V, but if you can run the 328p at 3.3V then I believe you can use it. If I understand the datasheet snippet posted by @JohnRob , then the minimum voltage for the 328p to read a '1' is 0.7*Vcc, which at 3.3V works out at around 2.31V.