3. MAX232 Wiring

The MAX232 chip is used to convert the 5v of your board to the 12v of your DB9 serial connection. 

You will need: 

Five 1uf capacitors 

Black, red, and two other colors of breadboard wire

Your soldered DB9 male connector

DB9 Gender changer

Here is the wiring diagram for the MAX232 Chip:

Image From: www.alldatasheet.com

Note: the RX-out wire connection from the MAX232 should be plugged to the TX-in pin on your Atmega324p (pin 15) and the TX-out from your MAX232 to the RX-in pin of your Atmega324p (pin 14).

The RX and TX wires you soldered to your DB9 adapter plug to the RX-in and TX-in pins of the MAX232 and the ground wire connects to the ground rail of your breadboard. 

Use the gender changer to change the male end of the DB9 adapter to female so it will plug to your RS232 cable. 

Detailed drawings coming soon.