Simple RS232 Serial Interface

Current Part:

PIC 18F4520 Microcontroller
7805 +5v Regulator
DB-9 Connector
Serial Cable
8x LEDs
16 MHz Crystal
10kΩ Resistor
Jumper Wire
9v Connector

Parts List Details
           Hopefully you are already familiar with most of the parts listed above. If not, don't worry, I've described the key components in more detail below. These are all the parts that make this system work.

PIC 18F4520
           This is the main microcontroller that is used to receive and send RS232 serial commands for the circuit. It will also control which output LEDs are set when commands are received. You could call this the 'intelligent' part of the circuit. The PIC 18F452/18F252 can be substituted for the 18F4520.

           This IC translates the digital +5v - 1's and +0v - 0's into the standard RS232 voltage levels. RS232 communication uses different voltage and current levels than 100% pure digital communication, so this translation step is necessary.

16 MHz Crystal
           This is the frequency at which the PIC will run. The instruction cycle is actually Fosc/4 -> 4 MHz which is blazing fast as far as we are concerned.

+5v Regulator 7805
           This regulator is used to maintain the +5v needed for the MAX233A and 18F4520 IC's. It is a good and simple 3 pin regulator.

DB-9 Connector, Serial Cable & Laptop/Desktop
           The DB-9 connector makes it easier to connect the cable to the MAX233A's outputs so I recommend buying one, they're cheap too! Naturally, you will also need a laptop or desktop that has a serial port connection. A simple terminal program will be used to send/receive commands to the PIC from the Laptop/Desktop.