How-To: Super Simple Serial Terminal Sep 16, 2008, 22 :01 UTC (3 Talkback[s]) (5201 reads) (Other stories by Adam Harris)
"For this How-To we'll be using an ATMEGA128 running at 16MHz. Since this device will be communicating through RS-232, we're going to need a level shifter. RS-232 uses 12 volt signals which will fry our 5V microcontroller. To fix this problem, we're going to use a MAX233 chip."