Parallel Port


Parallel Port Tutorial

This tutorial will help you get a taste of controlling your machine using the printer port. Though the parallel port isn't being used for many applications ,it is a boon for us hobbyists. This tutorial's main aim is to get you working ,so that you can send signals from the port like control a motor. Taking inputs from the port will be covered in a subsequent tutorial.

Parallel Port Anatomy:

Following are the pinouts:



Parallel Port DB25 Connector input and output

Picture Courtesy :: Ian Harries

The Pins having a bar over them ,means that the signal is inverted by the parallel port's hardware.If a 1 were to appear on the 11 pin [S7], the PC would see a 0. The Status pins are mainly used by the PC to know the status of the printer ,like if there is paper in the printer, end of paper etc.

Only the Data Port will be covered in this segment.

Parallel Port Female Connector

The Data Port

Sending commands involves only the data pins [D0 to D7].Though it is possible to use the some other pins as input, we'll stick to the basics.

Please remember that the Data pins are from pin 2 to pin 9 and not from pin 1.

If you have a good eyesight, check your parallel port connectors. Both the connectors [male/female], have numbers etched next to their pins, so people like us don't screw up our ports, connecting them the wrong way.The word "Parallel" denotes sending an entire set of 8 bits at once to the PC [That's why term Parallel Port].However we can use the individual pins of the port ; sending either a 1 or a 0 to a peripheral like a motor or LED.

Sending Commands to the Port:

This part is easy.Just a single line of code does the trick.

#include {dos.h}
[Please replace the {} bracket to <>]

void main(void)

{ outportb(0x378,0xFF); //da line

That's it ,you just set all your data pins to 1.

Led and resistor for the Parallel Port


If you take an LED and put one terminal at pin2 and the other to pin 18,it would glow.[Use a 2K resistor in series with the LED, otherwise u'll end up ruining your LED, or source too much current from the port pin]

if you wish to switch it off. Type this:


instead of the above line.(da line)

What did you do?:

0x378 is the parallel port address . Usually this is the default address.Sometimes it is 0x278 too

0x00 is the command appearing at the output pins. The Format is in Hexadecimal

So if u want to make pin no2 high, that's the first pin you type

0x01 which would mean 0000 0001 for the data port.

0x04 would mean 0000 0100

0x55 would mean 0101 0101

0x0A would mean 0000 1010

see the table below for reference


That finishes your basics so that you can run your motor.

Material to control a Motor via a parallel port:

Before trying out anything ,please remember that your parallel port is not meant or designed to handle more than 5Volts.If possible , trying accessing your parallel port using Windows 98.Windows XP does not allow access to the parallel port. You'll need special drivers for that.

Steps to Control a Motor:

Connect your motor to your Motor Driver L293D


Connect your parallel port pins to your Female connector [on your PC],through the male connector as follows

Commands for the motor




[Please replace the {} bracket to <>]

outportb(0x378,0x00); ---------STOP MOTOR
outportb(0x378,0x01);---------MOVE MOTOR(CCW)
outportb(0x378,0x02);---------MOVE MOTOR(CW)
outportb(0x378,0x03);---------MOVE MOTOR(Break!)
return 0;

The Sleep(n) function tells the port to hold [Latch] the command for (n) seconds.
eg: sleep(2)------------------delay or sleep for 2 seconds
If you want to work in milliseconds ,use the delay(n) command
eg: delay(500) --------------delay for 500 milliseconds

That's it, you can now control a motor using the parallel port.
Use 2 motors and you have a moving machine.
You can actually control the motors using the arrow keys using the Bioskey()
function. Check "C" help for this.


Original by mario.pieri

Try searching here:  


Look our Blog: Parallel Ports Blog
Forum: Parallel Ports forum
PCI Parallel port cards