Tutorial: PC Parallel Port Interfacing Techniques - Part 1

[xheavenlyx]

PC Parallel Port Interfacing Techniques - Part 1

6 October 2006 v1.0

Article: 2 Elec: 3.5 Comp: 3 Mech: 0

Introduction


In this tutorial I will just introduce the PC Parallel Port and how to identify its address for use in home electronic projects. Mind you the whole process and learning takes time but is fairly easy too! Remember, if you are interested then keep learning and trying new things. Fill me in if you have any questions or suggestions.

The Parallel Port is the most commonly used port for interfacing usual devices like printers and scanners. It's found commonly on the back of your PC as a D-Type 25 Pin female connector. But did you know it can even be used to make home made projects?

This port will allow the input of up to 9 bits or the output of 12 bits at any one given time, thus requiring minimal external circuitry to implement many simpler tasks. These outputs can act like switches in some cases or simply to light up LED’s. The inputs on other hand can act like pushbutton inputs to your PC.

Here you can see what the individual pins stand for.

*

Now for your Printer Parallel Port to work with a printer, it uses internal software to initialize a protocol for smooth communications. We won’t go into the details of this since it has about 5 different modes of protocol. All we need to know is how to connect your little lights and switches to your printer port with the most basic mode!

Hardware Properties

Scroll down for the table of Pin Outs Here for clear explination.

The output of the Parallel Port is normally TTL (Transistor-Transistor Logic) logic levels. The voltage levels are the easy part. The current you can sink and source varies from port to port. Most Parallel Ports can sink and source around 12mA. However these are just some of the figures taken from Data sheets. They vary quite a bit. So be careful not to overload your Printer Port.

Port Addresses


When the computer is first turned on, BIOS (Basic Input/Output System) will determine the number of ports you have and assign device labels LPT1, LPT2 & LPT3 to them. Usually the address for LPT1 is 378h.

To know your Parallel Port address, do the following:

Go to Start > Control Panel > System > ‘Hardware’ Tab > Click on Device Manager > Look for ‘Ports’ in the device list > Double click on LPT1 > Click on the ‘Resources’ Tab. In that you can see the starting address of I/O Range. That’s your number!

This address called the Base Address which points to a byte is used to send commands to your Port.
Read more on this if you are interested and in due time I will come up with another Tutorial on how to make some projects with this tool!

Sources:
http://www.beyondlogic.org/index.html

http://www.lvr.com/parport.htm

================================================== ==========
PART 2 of this tutorial : PC Tutorial: Parallel Port Interfacing Techniques - Part 2
================================================== ==========
-----------------------------------------------------------------------------
NOTES: The points below the title mean how Advance a Tutorial is in each field. 1 being easy and 5 being very advance.
*The above picture has been taken from: http://www.lammertbies.nl/ Thanks a lot

Feel free to ask questions or give sugestions!

[The_Big_K]

Great job, xheavenlyx. The discussion thread is open for questions / answers and feedback.

With more articles like this, we will have a separate section on CE for sure. Initially, we may not have lot of response for articles. Keep the spirit high !

-The Big K-

[xheavenlyx]

HAy biggie, i need to ask you something. Why didnt you put in PM service? What if I have ton send in some private coments or something?

And yea, I think you should remove the Comp, Elec and otheer Sub Forums because usually when we reach the Main Technical Threads, we dont see the Sub-Threads,not in sight or we dont concentrate. Else you can include the Sub-Threads in the Technical too.

I guess otherwise remove the Technical totaly and keep those discussions in General Sciences.

I know Im asking too much but it confuses me where to post my articles!

Regards and have funn

[The_Big_K]

(handles the questions one by one)

Why didnt you put in PM service? What if I have ton send in some private coments or something?

It is there. Available to members with 50+ posts & the special contributors.

I know Im asking too much but it confuses me where to post my articles!

Don't worry at all. Drop them in Technical Discussions. The forum structure is evolving and you can expect many changes. However, we will continue to add more trade-specific sections.

We will have a dedicated place for articles. In the meantime, let the technical discussions flood with your articles!

-The Big K-

[ash]

Oh man, I think this thread is underappreciated. Nice tutorial xheavenlyx! Is there Part 2 for this? I have an LPT port on my old laptop, but I have never used it for anything before.. it'll be cool to use it for projects. But, Im told that for example, the RS232 port in laptops don't supply enough power for serial programming with other microcontrollers. Does this limitation apply for parallel ports on laptops too?