please dont rip this site

Null Printer Adapter for Parallel Port

Copyright Tomi Engdahl 1996,1997

This circuit is a simple adapter for PC parallel port to think that there is a printer connected to computer. This adapter is useful for testing printing speed with different software and as a part of your own designs.

You can use this circuit to connect your simple circuits to the parallel port. Usually many home-made circuits use parallel port in a way which you have to use direct I/O commands to control the parallel port to be able to communicate to your circuit. Unfortunately this approach is not always possible, because some operating system prohibit the programs to directly control the computer hardware. In this situation you might want to use standard operating system printer printing functions for sending data to your circuit, but it does not work because your circuit does not generate the handshakes that are needed.

With this adapter you don't have to worry about generating handshaking signals in your own circuits. This simple circuit consists of only few wires connected to parallel port connector and it makes the computer to think that there is a real printer connected to parallel port and accepting the data.

Circuit operation

This circuit works using following principles: Bysy and paper out signals which normally come from printer have to be kept low, so they are tied to ground. Select and error signals which normally come from printer must be kept high, so they are connected to reset output in parallel port. Acknowledge signal is directly driven from strobe line.

Circuit diagram

Connecting diagram ASCII presentation:

1 -> 10

11 -> 12,18

13 -> 15,16

KILLspambarnermarkspam at Says: " Connecting pins 11 and 12 to any Ground pin (p18 to p24) will suffice. No need for greater complexity. Just fool the computer into thinking that the print has paper (-POK) and is ready to print (-RDY), that's all! " +

See also:

file: /Techref/io/parallel/null.htm, 4KB, , updated: 2013/7/10 14:09, local time: 2017/3/30 11:42,

 ©2017 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?
Please DO link to this page! Digg it! / MAKE! / 

<A HREF=""> Null Printer Adapter</A>

After you find an appropriate page, you are invited to your to this massmind site! (posts will be visible only to you before review) Just type in the box and press the Post button. (HTML welcomed, but not the <A tag: Instead, use the link box to link to another page. A tutorial is available Members can login to post directly, become page editors, and be credited for their posts.

Link? Put it here: 
if you want a response, please enter your email address: 
Attn spammers: All posts are reviewed before being made visible to anyone other than the poster.
Did you find what you needed?

  PICList 2017 contributors:
o List host: MIT, Site host, Top posters @20170330 RussellMc, IVP, James Cameron, Van Horn, David, Neil, alan.b.pearce, Josh Koffman, Sean Breheny, Bob Blick, Brent Brown,
* Page Editors: James Newton, David Cary, and YOU!
* Roman Black of Black Robotics donates from sales of Linistep stepper controller kits.
* Ashley Roll of Digital Nemesis donates from sales of RCL-1 RS232 to TTL converters.
* Monthly Subscribers: Gregg Rew. on-going support is MOST appreciated!
* Contributors: Richard Seriani, Sr.

Welcome to!