1. All About Serial

2. 2 different standards
There are 2 primary standards for serial communication
RS232
TTL/CMOS
RS232 is used by computers while most microcontrollers operate using TTL
Read the pdf RS232 vs. TTL for a more technical description of the different standards

3. How to translate
Read over the document entitled Sparkfun Serial Communication
We will run through the experiment utilizing the Max232 chip to convert from RS232 to TTL
To make life easier use the MAX3232 breakout board from Sparkfun available here:

4. Experiment Materials Arduino Uno or Duemilanove with AVR chip removed
USB to Serial adapter and cable (from Lesson 1)
MAX3232 breakout board
Jumper wires

5. Procedure Wire the circuit as shown in the Sparkfun pdf
Looking at the breakout board schematic will show that all necessary capacitors have been installed for you so it is only necessary to wire directly to power (the 5 volt and ground lines from the Arduino)
Connect the ground on your broken out RS232 cable to the Arduino ground
Install Tera term (link is on course site)
Open Tera term using default settings for both your Arduino COM port and your USB serial COM port

6. Continued
If everything is wired correctly you should initially see whatever you type through the Serial adapter displayed in the same terminal window (when wired in loop-back mode)
Next wire in the Arduino and now whatever is typed in one terminal should appear in the other and vice-versa

7. Circuit Picture