fungus:
falcon74:
Would I still have to worry about polarity inversion ?No. RS232 doesn't do inversion, I don't know where anybody got that idea.
I don't know where you get that idea from, but please check this link:
https://www.sparkfun.com/tutorials/215
The RS232 voltage level signal IS inverted from the TTL level version.
EDIT: An RS232 line idles at -12V nominally, a TTL line idles at +5V. Some micros (I don't know about the AVR) will let you invert the signals that the hardware UART generates. This will sometimes work with the more modern serial ports, but I assure you that there is a whole lot of vintage equipment that will not honor +5V and 0V signals, even if they are the right polarity.