Using a PC's parallel port for more than printers- ele1pp

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Using a PC's parallel port for more than printers

This material is about the parallel port on MS-DOS / Windows computers. It sometimes spills over into things of more general nature when talking about devices you might attach to the parallel port. In a moment, I am going to ask you to consider if the parallel port is really the way you want to go, and suggest alternatives... but first....

PLEASE NOTE: You CAN damage your computer if you make ill-advised connections to it.
Any use you make of anything you find here must be AT YOUR OWN RISK

I have designed a parallel port protector that may be of interest. (Click on the link for information, and a way to obtain the circuit diagrams.)

For a free "turn parallel port pins on/off" program, which works with Windows XP (and other Windowses, I think) check out my page about SheepdogCurtainCloser.

Also, as part of my Delphi tutorials website, I have posted another small app to turn individual pins of the parallel port on or off. You can download the .zip archive that goes with the tutorial. The app is in the .zip... you don't need to be a Delphi programmer to use it. But you do need to put both the app (DD79.exe) and the dll called "InpOut32.dll" in some folder on your system. They should be in the same folder.

For any I-Want-It-Now merchants: A good site with essentials, minimal warnings, fewer details. (Not written by me. Opens in new tab, so you can come back here if disappointed.)

Table of Contents, Parallel Port Use......

A few odds and ends
Alternatives: "New" ways to do the things we did with the parallel port in the Good Old Days.
How to send and receive data to/ from the parallel port.
You can defy Bill Gates and send/ receive data even on a Win9x, NT or XP machine!
Which pins (both back of computer and end of cable) have which signals.
Help on the software issues, with Basic, Pascal and Delphi addressed.
Help connecting an LED, for the complete beginner. (Opens in new tab)
Help with inputs and outputs, for beginners.
Help with the issues of load limits, pull ups, pull downs.
USB or the serial (COM) port: Notes on interfacing.
USB Parallel Port Adapter: Fine for printer, maybe.
..... AND a way to email me, for whatever I've missed!

Odds and ends...

Before we get to the parallel port stuff, two ads from our sponsors...

1) If you are going to use this page, you are probably not a computing novice. Ever set up a web server? It isn't hard! If you have an always- on broadband connection, FarWatch may be of interest. I have written pages for you explaining how to use an old Win98 box (or better) to give yourself a way to monitor the premises the old Win98 box is at from anywhere on the internet. Nothing to buy! And if you connect something to that PC via it's parallel port, you can "see" the state of the inputs to the parallel port from afar, too.

2) If you would be willing to help bring this information about the parallel port to a wider readership, please check out my plea for translators?

Don't want to tie up your printer port? No excuse!! You can get a cheap card to provide a second parallel port! Alternatively, for some projects needing input only consider using your joystick port... it can detect 4 switches and 4 resistances. (N.B.: Most joystick ports do not sense analogue voltages.) For how to program Delphi 2 and higher to read joysticks visit this page of my Delphi Tutorials.

Using your PC isn't the only way to have a lot of fun with controlling and sensing external devices, for example the Arduino, an inexpensive programmable microcontroller, which is itself open source, and which has excellent free, open source development hardware. http://www.controlplus.nl/ (Control Plus) once sold a neat little Pascal based microprocessor system, and they offered a free simulator. If you hear of that being available again, please tell me? If for some reason you don't like the Arduino, there are alternatives.

Don't let the warning above worry you too much... I want to stress that there is a lot of fun to be had with electronics projects. Find yourself an 'antique' PC. If you can't rescue one from a dusty corner, you can buy one for almost nothing. You can use the same monitor as you use on your main machine. If you wreck the antique, it hasn't cost you much! (I got one, with monitor, off a sidewalk once!)

I have a third generation inexpensive 'protect the computer' circuit. You interpose it between your PC and the home-made stuff you are attaching to the parallel port, and any mistakes in the home-made things are blocked off from the computer by opto-isolators and relays. (Inputs to the computer are passed through an opto-isolator, outputs are fed to the coils of relays. Properly set up, the worst thing you can do is wreck an opto-isolator or a relay.... both relatively hard to do!) Email me if you are interested in that device. If you can design and etch your own PCBs I can send you some notes. (Send me a snailmail address, as they are not available in machine readable form.) If you are not making your own PCBs, I may still be able to help, but not so quickly and not for free.

If you are very new to the hardware side of computing, my Connect An LED In Words Of One Syllable may be of interest.

Alternative ways to have the fun we used to have via the parallel port

If you are sure you just want to know how to do it with a parallel port, without considering the alternative connection paths, you can skip over this "alternatives" section.

Once Upon A Time... it was quite easy even for a mere enthusiastic amateur to connect external electronic bits and pieces to a PC. Many of us started with LEDs (or even incandescent bulbs... there WAS a time before LEDs!). Then there were push buttons.... it wasn't only output that was possible. And once you got started, the sky was (and is) the limit. There's a saying: The hard part is thinking of what you want to do. In other words, the hard part is finishing "I'd like to make the computer control/ read.... "

It is still quite possible to do these things... but it isn't quite as easy today.

If you are just getting started, I would advise you to consider other ways of doing the things we used to do via the parallel (or serial) port. They won't be suitable for all of you, nor for all projects, but at least consider them. And when I've listed them, I will go on to talk in detail about how to use the parallel port, for those who want or need to do it that way.

You can now (2010) buy into the fun world of microprocessors for not very much money and perspiration. I particularly like the Arduino, but there are many alternatives. (I have an Arduino-specific page which you can access from the microprocessors page there is a link to above.) Once you master the basics... not rocket science... you can use an Arduino, or similar system the way we used to use a PC and its parallel port. Life becomes fun again, instead of being work. Once upon a time, I had a whole PC tied up just to run a burglar alarm at my house. Now the same work can be done with an Arduino. The Arduino costs MUCH less, uses less electricity, is more tolerant of the occasional power failure.... and has other virtues, few vices.

Another cool possibility: You can connect one or more! 8 bit input/ output ports to your PC using the Dallas Microlan, aka "1-wire". Look at the DS2408 if you are impatient. Or, give my introduction to 1-Wire a try. Extra cool: The ports would interface to your computer via provided-by-others software running through either your serial port or your USB port!! (You still have to access the software that accesses the ports, but a lot of the overhead of the communications with the port is taken care of for you.)

The bad news? You need to equip your PC with a pc-to-MicroLan adapter (about $25). The data rates wouldn't be as high as they could be via a PCs parallel port... but they will be high enough for many designs. You will need more advanced programming skills to use the 1-Wire "answer".

Digital I/O over a LAN, or even over internet: We are now moving into a more expensive and less flexible realm, but there are ways to have digital I/O pins (what a parallel port gives you) connected to a PC across a LAN that the PC is part of, or even across the internet, if you are willing/ able to set up a server near the device with the I/O pins. I don't have extensive information for you in this area, but I do have some. See my pages starting with Sensing and Control across networks. There's also my FarWatch system, which is not expensive, for what it does, but doesn't offer you all the possibilities of what you can do via the parallel port. FarWatch is mainly for monitoring premises from afar... you can check temperatures, switch closures, etc. You can even have graphs of the state of the monitored phenomena.

The Arduino, already mentioned, is one way into the delightful world of digital electronics. If you are already in that world, you might consider at least the following two "answers" to the sorts of things we used to do with a PC and its parallel port.

There is a PIC microprocessor from MicroChip with built in USB services. It looks like a neat device for all sorts of things. I haven't played with it personally, but know people who have. It looks like it shares many of the Arduino's virtues. I suspect you need a little more experience or determination to get started with it, and creating your own USB devices will never be trivial, but if you want to give it a try, you should look into the PIC 18F4550. The Sparkfun experimenter's board looks like a fine solution to the hardware issues. ($38 at 2/10)

Another possible route: If you are into making your own electronic devices, you might be interested in the USB modules from www.ftdichip.com's products page.

I wrote the next paragraph a while ago... and now (3/10) am not sure what device it describes! I think it is the FT2232H from FTDI, but I'm not sure, and after 15 minutes of struggling around their site, I've given up trying to find what I saw previously, somewhere. If it sounds good to you, do go to FTDI's site.... I think you will be rewarded!

For about $20, you can buy a little unit that plugs into a Win98 or higher machine via USB. On the "outside world" side, it has 8 bi-directional digital input/ outputs, and a few handshake lines. The programming isn't trivial, but there is great material about accessing the device. Illustrations in Delphi are provided. You either install a TComPort component (a freeware one, with Delphi source code is available from Dejan Crnila and then access the 8 bits as if (to Win98) they were on a COM port, OR you use a DLL (supplied royalty free from FTDI). It is not exactly a parallel port via USB, but that's roughly the idea.

ANOTHER "answer (!!): There are now devices which might be called "parallel ports on the LAN". And if you can access something on a LAN, you're not far off being able to access it across the internet, too, if you want to. Turn up your home's heating via the internet as you shut down your PC at work at the end of the day? Why not!! Etc.

One source of interfaces accessible across LANs is WizNet. That link will take you to the product page of their, to adapt their online text...

Webserver based IO control module

Key Features
  - Remote I/O Monitoring and Control with Ethernet
  - 8 Digital Input Ports
  - 8 Digital Output Ports
  - 2 Analog Input Ports (12 bit resolution)
  - 2 Analog Output Ports (12 bit resolution)
  - Supports Application Program
  - Supports WebServer

I found several suppliers (search with Google for "WIZ220IO") selling it for a little under $40 (6/10).

And so, at last, to Doing It With A Parallel Port... if you haven't been convinced to use one of the alternatives above, that is!....

Quick guide... extended explanations appear further down the page

Software...

For a simple program to turn bits on or off just by clicking a button, go to my shareware site. There are free programs there... some for toggling or reading bits, including one for electronic time measurement via the parallel port, or via a joystick's "fire" buttons.

To send 123 to the parallel port....

(There are notes below about obtaining Delphi)

Once upon a time, sending 123 to the parallel port (or reading from the input bits there) was a pain. The way to do it depended on what Delphi you used and what OS the program had to run under. No longer, hurrah!

Some time ago, a kind reader sent me an email saying... "use inpout32.dll. It enables the sample programs in Jan Axelson's book Parallel Port Complete".

Click here for Jan Axelson's site, www.lvr.com (Link okay since before 3/05). It offers help with:

Information and tools relating to parallel ports,
RS-232 and RS-485 serial communications, 8052-Basic,
Microcontrollers, and making printed-circuit boards.)

It took me a while to get over my fear of DLLs, but am I glad I did! They are no big deal.... used in moderation. Details are given in my tutorial on using inpout32.dll. That is written for Delphi programmers, but C or VB (yuck) programmers will find help there, too.

If you use inpout32.dll (freeware, dll and source code available from Logix4u), then one version of your program will run on many different operating systems... Win 3x to XP at last count, including NT. (My software for XP relies on this dll.)

=============
The page you are reading has been around for a while. Way back to MS-DOS days in fact. In February 2010, I moved information relating to using the parallel port with old software under old operating systems (pre-NT) to its own page.

----
A newsgroup post said that in QuickBasic you do the following. This probably only works on pre-Win98 systems.

    Out &h378,123

The &h378 is just another way of saying 888. The &H part says "what follows is written in hexadecimal (aka "hex"). Hex 378 is the same as decimal (our "normal") 888. It's like the "difference" between "12", "twelve" and "dozen".

----
For NT, XP, etc, if you don't want to use the better way (using inpout32.dll, explained above), you first need to install a port driver. Here are a few URLs you could explore:

    TVicHW32       http://www.entechtaiwan.com/tools.htm
    DriverX
    Tinyport (NT only)

(How to access the other lines of the parallel port is covered further down the page.)

Next, a little "side-bar", probably in the wrong place, but maybe you'll find fun:

To control 8 lights from a parallel port or 8 pins of a microcontroller is eXTReMely easy. If you want to control more, you are going to have to design some external electronics with "latches". Three lines from the parallel port will go to something like a 74138 which selects one line of 8 outputs from the 74138 according to the pattern of ons and offs on the three inputs to the 74138. You will also use one line of the parallel port to say "latch now, data is valid", i.e., the signals you're seeing are the signals I want you to notice. This "latch now" signal is how you avoid problems while the signals are changing. The remaining 4 lines from the parallel port will be data lines. Thus, you will be able to change the state of four lights at a time, but you will have 8 banks of four lights, so the circuit, potentially, could have 40 lights (or other output devices) on it.

Hardware

Imagine you are looking at the back of your PC, and that the parallel port socket is horizontal, with the long row of socket on top. The numbers of the sockets at the ends of the rows are...

13  . . . . . . . . . . 1

    25 . . . . . . 14

(See below for where things are to be found on the connector at the end of the cable normally plugged into a printer.) The 'interesting' pins are:

Data bits 0-7: Pins 2 to 9, respectively. If you write to address 888 (decimal), you should see the outputs on those pins change. (The address is different in some circumstances, but try 888. In the "good old days", you could simply use the following Borland's Delphi or Turbo Pascal:

port[888]:=254

would set all bits but the first one high.) See my page about InpOut32 for how you read and write to the correct places today. The NUMBER you get, or write, hasn't changed.

Pins 18-25: Signal ground. (I.e. for a VERY simple experiment, connect an LED to pin2, a 680ohm resistor to the LED, and then the other end of the LED to pin 19. If it doesn't work... try turning the LED around!)

Inputs: If you read address 889, you can discover the state of 5 pins. They determine the state of bits 3-7 of 889. bTmp:=port[889] was the old 'raw' Delphi or Pascal you needed. Obviously, you do clever things with the result of that. The bits are mapped and named as follows:

Bit Pin Name
3   15   Error
4   13   Select In
5   12   Paper Empty
6   10   Acknowledge
7   11   Busy

(A trap for the unwary... 'Busy' is inverted 'just inside' the computer. Thus if you apply a '1' to all of the pins, you'll see 01111xxx when you read 889! Isn't computing fun?)

Before turning to more generally useful things, I might as well finish off the other pins....

Write to 890 to set the state of the following pins:

Bit Pin Name
0    1   Strobe
1   14   Auto Linefeed
2   16   Initialize
3   17   Select Out

The rest of this page is rough.... but ready.

The layout is a mess (sorry), and there's more editing to do (you're welcome) but there's a lot of good info and links below and on the linked pages....

With a way to read or write to the parallel port, and a few LEDs and switches, you're set to have some fun. You can go a lot further, if you want to add other sensors. (More on sensors at Sheepdog's Sensing and Control site.)

For many projects, you need a source of 5v (or 12v) for the electronics outside your PC. I saw the following in a newsgroup. See my note at the end before attempting the test described.

"If you're getting the 5V from your PC, the ground from the PC will be fine. However, if you're trying to add 5V from somewhere else, be just a little wary. The PCs logic ground (and thus that of your one-wire bus) is probably tied to either line neutral or line ground. If you use a non-isolated switching power supply to get 5V from house wiring, it's possible to make smoke under certain conditions. If you're not sure, hook a cheap 1K resistor between the PCs ground and the ground of the power supply you intend to use (don't connect 5V yet for this test). If the resistor doesn't immediately go poof, then hook a voltmeter across it and check on both DC and AC settings; you shouldn't see more than a small fraction of a volt this way. If this test shows little or no voltage across the resistor, you're probably all set. Not all bad to put a very low-wattage 10 ohm resistor in both the ground and 5V lines, though - that's really cheap insurance, and most times the resistors will sacrifice themselves and protect the rest of the circuitry if something's badly amiss.

"As always, experiment at your own risk. Safety glasses are a minimum precaution when you think there's a chance of blowing up a resistor! Guard your eyesight carefully, and be prepared to turn off the power quickly if anything untoward develops."

I'm not sure why the writer suggests the 1k resistor. I would be inclined just to put the leads of my voltmeter on the two unconnected grounds, hoping to find no voltage (DC or AC!) between them. The 10 ohm idea puzzles me too.. why not just use a fuse?

In response to the previous paragraph, a test engineer in a Swedish firm kindly sent me the following....

Much good information is available in the British magazine 'Everyday with Practical Electronics.' You can visit them at www.epemag.wimborne.co.uk

Robert Penfold's 'Interface' column has frequently had projects interfacing all sorts of things to the parallel port, but I don't think much of his material is in the website... yet. Agitate!

===
Someone asked: Why do we need to connect pull up/ down resistors or hex inverter buffers (open collector) to the control pins of a port? What is open collector actually? What are the states of the open collector port?

Someone answered:

Inputs do NOT *HAVE* an inherent state, and need NO pull-up or pull-down! But the input voltage to them must be definitely HI or LO. The open-collector outputs have internal pull-ups, and do NOT *NEED* external pull-ups, unless the internal pull-up is not sufficient. Rarely true!! See my FTP Gateway's TUTS/totmpole.tut file for explanations of how the three different kinds of outputs work. See the simplpt.faq and other *lpt.faq files for information about the parallel port. The simplpt.faq is below, Steve

ftp://ftp.armory.com/pub/user/rstevew
The filenames are: *lpt.faq; ibmlpt.faq, tomlpt.faq, and krislpt.faq. each meets different skill levels and needs.

===
If you are very new to digital electronics, I offer you a tutorial on inputs and outputs.

===
If you put eight LEDs, one on each of pins 2-9, then you can get a pretty little light show very simply. The following is pseudo-code... you should be able to convert to the language of your choice....

REPEAT
  Datum=0    ;Don't use a byte-type variable. Integer will do.
  REPEAT
    SEND Datum to parallel port
    ADD 1 TO Datum
    (If using Delphi, put application.processmessages here)
    WAIT A BIT
  UNTIL Datum>255
UNTIL 4=5 (i.e., forever!)

===
Someone wrote me with a question about using the "strobe" output. I sent the following in reply; maybe it clears something up for you....

The following is untested and may have silly mistakes, but should be a guide. Port 890 is read first, and then OR's or AND'd with the values given so that only the "strobe" bit is set or cleared. (You'll have to adapt the program to read and write the port the "new" way. ":=port[809]" and "port[890]:=" were the old ways of doing read and write.

procedure SendStrobeHi;
var b1:byte;
begin
b1:=port[890];
port[890]:=b1 OR 1;
end;

procedure SendStrobeLo;
var b1:byte;
begin
b1:=port[890];
port[890]:=b1 AND 254;
end;

Although the name 'strobe' implies a pulse, the output from the parallel port (pin 1) should stay high after a call of SendStrobeHi until you make a call of SendStrobeLo, after which it should stay low, etc. Try sending the pin high and low with nothing but your voltmeter attached.... maybe the circuit you are trying to drive has flaws? (The strobe output from the parallel port shouldn't be expected to drive much.)

===
Some readers have reported problems when trying to drive a laptop's LPT with port[888]. (And other computers may be using a non-standard port, not just a laptop.) I too have had the experience, though in my case, I did not explore the situation. I may just have had a situation where I was wanting too much current from the output.

===
The pinout at the printer's end of a printer cable is as follows...

Look into the end of the cable that is normally plugged into your printer. Turn it so that the long side of the connector is on top.

'Pin' 1 will be the one at the upper left.
The first in the lower row is 'pin' 19.

I won't persist in putting the word 'pin' in quotes (to acknowledge the fact that the connections are not literally pins}... assume them for the rest of this discussion of the printer end of a Centronics cable.

Pin 2 is an output, the LSB of the data byte.
The next pins (3,4,5...9) carry the rest of the byte, in ascending order.
Pins 20-27 carry the corresponding 'data returns', i.e. are signal grounds. In a perfect world, I think you are supposed to connect to each of them, but I believe they are all connected inside the computer anyway, so you can probably use just a few. (Using more than one takes care of any current limitation issues, and provides insurance against bad connections in the system.)

I can provide details of where the other signals are if you need them.

===
Remember 'the' PC is not always made exactly the same way... and, especially with old machines, a bit may be damaged or not implemented. Experiment! Be sure to test things as you go along, 'bottom up.'

The previous paragraph applies in particular to the issues of the power capabilities of the outputs, and the pull- up/ down needs of the inputs. I'm a novice on these issues myself... but I do have several machines doing useful things for me. In general, I wouldn't be reluctant to try to drive the base of a transistor with an output. I try to design the external circuits to be fail-safe... e.g. if the computer that controls my burglar alarm is off, or if it has booted into MS-DOS but not my alarm software, the output of the parallel port in those conditions was taken as the starting point for the circuits that ring the alarm's bell. My program moves the output away from the 'default' state to ring the bell. (There are also less complex circuits also attached to the bell which can ring it if the computer is dead!)

I have driven LEDs directly from the parallel port in my machine.... but I wouldn't assume that every machine has sufficiently strong outputs. AND BE SURE TO INCLUDE a resistor in series with the LED whenever you use an LED, be it with the parallel port, or otherwise.

(For the barely-started: Do be careful not to connect more than 5v to any input, and NOT to connect 0 or 5v directly to any output. There should be significant resistance between an output and either 0v or 5v, e.g. the resistor mentioned in my simple experiment with the LED, above.)

I've had enormous fun with circuits driven off the parallel port. Getting started can be a little hard, but you'll soon be under way.

See also: The Arduino project has a whole page full of neat ideas which would be of interest to people who are interested by what I have in my pages. The pdf document about driving relays is especially good, and address issues that come up again and again in discussion forums.

===
Here is a version which will compile in Delphi 2, for Windows 95 and higher. It may also work with NT. (While I think this works, I would go the InpOut32 route, described above.) The form has a Timer on it. The timer's interval property is set to 2000. The only other thing the form needs is a label called Label1. Below is EVERYTHING you need from 'implementation' through to the final 'end.' It will need adapting, if you want to use it on a post Windows98 machine, but only the parts which

implementation

{$R *.DFM}
{$R+} {nothing to do with previous $R}

(*The Delphi 2 on-line help has an entry for Mem[<seg>:<offset>], but
  the compiler does not seem to recognize it, not does it appear in the
  Reference Library Guide. Various postings in usergroups
  seem to say that Win95 will not let programs access physical memory.
  There was also an entry for something called ExtEscape which looked
  promising for sending something to the port, but I haven't explored
  that yet, and it didn't appear in Reference Library Guide either.

 Peter Below (TeamB) provided the following port access routines
 in a newsgroup post. He said push and pop were not needed, that
 they were in fact bad ideas. He pointed out that the function uses
 the normal Delphi 2/3 register calling convention and thus will get
 the first parameter (e.g. IOPort) in eax, the second in edx.

 In addition, he said...
 This will not work on NT; it works on Win9x only because the OS has a
 generic port driver. For NT you need to install such a driver first.
 Here are a few URLs worth checking:
    TVicHW32       http://www.entechtaiwan.com/tools.htm
    DriverX        Tinyport (NT only)

    procedure PortOut(IOport:word; Value:byte); assembler;
    asm
      xchg ax,dx
      out dx,al
    end;

(*More, similar, routines from Peter Blow. They are not needed
  in this simple demo program...

    function PortIn(IOport:word):byte; assembler;
    asm
      mov dx,ax
      in al,dx
    end;

    function PortInW(IOport:word):word; assembler;
    asm
      mov dx,ax
      in ax,dx
    end;

    procedure PortOutW(IOport:word; Value:word); assembler;
    asm
      xchg ax,dx
      out dx,ax
    end;

End of material from Peter Blow*)

procedure TForm1.Timer1Timer(Sender: TObject);
begin
if bPoke<>0 then begin
   Label1.caption:='0';
   bPoke:=0;
   PortOut(888,bPoke);
 end(*no ; here*)
 else begin
   Label1.caption:='255';
   bPoke:=255;
   PortOut(888,bPoke);
 end;(*else*)
end;

end.

===
In a newsgroup, I saw: "the TDLPort IO 'wrapper' can be installed as a Delphi component. This allows IO under Win95/98 and (using a different file) Win NT. I know the latter normally blocks attempts to Write to/Read from specific addresses but the DLL (legally) get around the problem. I'm hoping that the Win95/98 version will do the same rather than just re-duplicate inpout32. It comes with a nice manual and is FREE!

Even though there was a lysdexic error in the above, Google found for me an article for me at www.delphi32.com containing....

Name: TDLPortIO 1.3 Date: 12/7/99
Environment: Delphi 3.0, Delphi 4.0, C++ Builder 3.0, C++ Builder 4.0 Download
Type: Freeware with Source Size: 851 Kb
Description:
TDLPortIO is a wrapper for the free DriverLINX kernel mode driver (included).
It allows full port IO under Windows 95/98/NT.
Comes with a C++ Builder and Delphi components,
ActiveX control (for Visual BASIC) and DLL version.
Compatible with the shareware package TVicPort.

===
I've started a collection for you of links and information about communicating via serial or USB ports. It is at... My Serial/ USB Port page

This isn't really the time or the place to tell you about the following, but until I can write it up properly....

I wrote the following a while ago... and now (3/10) am not sure what device it describes! I think it is the FT2232H from FTDI, but I'm not sure, and after 15 minutes of struggling around their site, I've given up trying to find what I saw previously, somewhere. If it sounds good to you, do go to FTDI's site.... I think you will be rewarded!

If you are into making your own electronic devices, you might also be interested in the USB modules from http://www.ftdichip.com/FTEval.htm. For about $20, you can buy a little unit that plugs into a Win98 or higher machine via USB. On the "outside world" side, it has 8 bidirectional digital input / outputs, and a few handshake lines. The programming isn't trivial, but there is great material about accessing the device. Illustrations in Delphi are provided. You either install a TComPort component (a freeware one, with Delphi source code is available from Dejan Crnila and then access the 8 bits as if (to Win98) they were on a COM port, OR you use a DLL (supplied royalty free from FTDI). It is not exactly a parallel port via USB, but that's roughly the idea.

Apologies to those of you who've read all of this page carefully... you will have seen this item above... but many people just skip web pages, and I want everyone to know I have designed a parallel port protector that may be of interest. (That page opens in a new window, so you won't lose this page... and it gives you access to the circuit diagrams.) It puts opto-isolators on 4 lines, so you can connect (almost) anything as an input, and puts relays on the other 4 parallel port lines, so you can send outputs to control things easily.

For Delphi programmers: Tutorial: A free DLL to access the printer port, and how to use it..

For Delphi 2 (and above) programmers: Tutorial: How To Access A Joystick.

USB cable for parallel port printer

Bad news, I'm afraid. You can buy a USB "parallel port" cable. It (may) work for connecting an old parallel port interfaced printer to your PC, but it won't be of much help to you for the sort of "bit bashing", digital I/O that all of the rest of this page is about... unless you can "get into" the driver software. If the cable is FTDI based, as it may be, you MAY be able to use it as a cheap source of an FTDI chip, but programming the ons and offs of individual bits is not trivial.

Sorry. It is an attractive "gotcha". I know, having fooled myself into trying one. But it Just Isn't That Simple, sadly.

Et Cetera

A page with this page's editor's eddress is available if you want to send feedback or ask a question about something here. (You can probably get faster and better answers to "How do I...?" questions via Google.)

Haven't found what you wanted to know about the parallel port? Click here to go to a further page consisting mainly of links to other resources.

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Ad from page's editor: Yes.. I do enjoy compiling these things for you... hope they are helpful. However.. this doesn't pay my bills!!! If you find this stuff useful, (and you run an MS-DOS or Windows PC) please visit my freeware and shareware page, download something, and circulate it for me? At least (please) send an 'I liked the parallel port use page, and I'm from (country / state)' email? (No... I don't do spam) Links on your page to this page would also be appreciated!

Click here to visit editor's freeware, shareware page.

Don't forget to check out the programs for writing to or reading from the parallel port at my freeware and shareware site. All of the software is only for Windows, I fear. Most of my software will run on anything from Windows 3.1 to Vista and probably beyond... but the ones that interact with ports tend to be restricted to "before NT (pr XP)" and "after Win98" because of OS issues determined in Redmond.

The editor of the page you are reading also offers you a general 'electronic projects' page.

Why does this page have a script that loads a tiny graphic? I have my web traffic monitored for me by eXTReMe tracker. They offer a free tracker. If you want to try it, check out eXTReMe's site

Page tested for compliance with INDUSTRY (not MS-only) standards, using the free, publicly accessible validator at validator.w3.org

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