Simple Parallel (Printer) Port Interface

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This is the basic interface I used as part of my Computerized Room project. This is the parallel interface only. The 8 bit input card can be found, along with the rest of the project, at Computerize Your Room/House. This interface, as well as the other two interfaces, came from the book "The Robot Builders Bonanza", by Gordan McComb. This interface is also useful for controlling small robots, etc. It is cheap and fairly easy to build, although you should not attempt this project unless you have prior experience with electronics. You probably won't damage anything if you hook it up wrong, but there is always a chance (some parallel ports are better protected then others). If possible, test the project on someone else's, or a school computer :-)


This is the schematic of the parallel port interface

Parallel Port Pin Assignments

Parallel port pin assignments graphic


Total Qty.
U1, U2, U3374LS367 Buffer IC74367, 74HC367
MISC1Case, Wire, Sockests, 18 Pin Socket (For Output), 25 Pin Connector (For Parallel Port), Ribben Cable


  1. I built the interface on a piece of universal solder board due to the large number of wires that must cross. It is also much easier to fix mistakes then on a PC board. I also used a 25 pin crimp connector to connect it to the parallel port. 26 conductor ribben cable was used to link the connector to the board.
  2. This interface only offers 5 inputs (on some computers it may be less). For more inputs, see Computerize Your Room/House. If you choose to use the inputs, remember that the voltage level can not exceed 5 volts or fall below ground.
  3. This circuit is TTL and therefor must be powered by no more then 5 volts.
  4. You can download control software from my files section.
  5. For more information on programming the parallel port, see Programming The Parallel Port In QBasic or Programming The Parallel Port In Visual Basic.

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Computer Controlled Frequency Counter/Logic Probe, Parallel (Printer) Port Interface


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Parallel (Printer) Port Interface
Wednesday, October 19, 2011 5:59:27 AM
I have some difficulties for vb6 program for parallel port communication. can any one help me by send me the complete code + dll files. thankx
Parallel (Printer) Port Interface
Saturday, December 04, 2010 5:15:59 PM
For effective and simple control of parallel port, check out LibertyBASIC. Port driver for XP and above is included with distribution and there is an excellent and supportive user forum with a hardware interfacing thread.
Parallel (Printer) Port Interface
Tuesday, November 17, 2009 4:13:37 PM
I'm exploring your site; it has great info. I built a small PCB with a ULN2003 chip driving reed relays to control my room lighting (dimmer) using the parallel port on my PC. It's simple and works quite well. I'd now like to add the ability to read the level of the dimmer and send this data to the PC. The dimmer has 4 LED's which I believe are 9VAC and are either on or off. I need to translate this to something that could be read by the parallel port and sent to an app on the PC. Any ideas?
Parallel (Printer) Port Interface
Thursday, September 10, 2009 9:44:08 PM
Verhy informative, Well done!
Parallel (Printer) Port Interface
Sunday, June 28, 2009 2:44:22 PM
is it passable to do this same thing using the usb port instead of the Parallel Port I have been looking all over the internet trying to find a schematic diagram on this if you have any information please let me know thank you Jeremy
kurdi muhammad
Using this circuit in Windows XP
Thursday, March 19, 2009 6:34:24 AM
You can download this dll file ( Inpout32.dll ) from and control your Parallel port even under Windows XP. Note: In Windows 2000 and XP and later versions of windows, you can NOT use the PPort directly . You must use a kernel mode device driver to that.......Actually inpout32.dll does that for you easily.
Parallel (Printer) Port Interface
Tuesday, March 03, 2009 7:16:47 AM
is it possible to use this interface to conect 2 computers for use with qbasic so that one way comuncation is possable
Black Hawk
Parallel (Printer) Port Interface
Saturday, February 21, 2009 10:33:47 AM
Dear Sir, by using any input, like 5v or getting 0v vich pins i can use to detect whether hardware is connected or not
Javad Ahamad K.V
Parallel (Printer) Port Interface
Friday, October 10, 2008 1:16:46 AM
I am very happy with your vb parallel port helped me a lot. i have a doubt? if we want to input data through status port by shorting it and ground how we can detect at the time of running? eg: i runned my program then when i set 88 form colour shoul be red,and if the value is 104 the form colour should be blue without exiting the program.what is the code for that? i tried like this, if vbinp(889)=88 then form1.backcolor=vbred elseif vbinp(889)=104 then form1.backcolor=vbblue end if this is working when it wrote under an event like click or keypress ect..... but i want to check continously without changing any event plz help me........
Parallel (Printer) Port Interface
Tuesday, October 07, 2008 8:44:50 PM
Sir pls give me a kernel driver for WindowsXP, im trying to access parallel port interfacing with Assembly Language Program using A86 assembler.. pls help.. im searching for so long..

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