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Parallel Port Central

The PC's parallel port, including ECP, EPP, bidirectional, and IEEE-1284 modes (and other I/O ports as well).

Basics | ECP & EPP | Hardware | Troubleshooting | Connecting 2 PCs
Using Printers | Programming

Parallel Port CompleteParallel Port Complete

For all you ever wanted to know about the parallel port, order a copy of Parallel Port Complete. Read Chapter 1 on-line.

The Basics

  • Jan's Parallel Port FAQ has answers to frequently asked questions about using, interfacing, and programming the parallel port in all of its modes.

  • The parallel port FAQ . Basics about the parallel port and how to use it, by Zhahai Stewart. (50K)

  • Control and data acquisition information and projects, from Peter H. Anderson and his students. Code examples in C.

  • Tomi Engdahl's PC Hardware pages. Many links.

  • Parallel Port Programming. An article from Hasha Perla.
  • External Parallel Port devices and Linux. Many links and info. From Tim Waugh.

  • If you have a (usually old) device that sends data to a line printer, and you want to instead read the data into a PC, buy or make a parallel-to-serial converter and read the data at a serial port, using a terminal emulator or software you write.

  • In Spanish: El puerto paralelo from Javier Olcina and David Romero.

  • Enhanced and Extended Ports

    Including the bidirectional (PS/2) port, extended capabilities port (ECP), and enhanced parallel port (EPP), and the IEEE-1284 standard that descibes them all.

    General Information

  • A table showing the pinouts of all three of the commonly used parallel-port connectors, including the 25-pin D-sub, the 36-contact Centronics connector, and the new IEEE-1284C connector. (6K PDF (Acrobat) file)

  • The title of the IEEE parallel port standard is 1284-2000 IEEE Standard Signaling Method for a Bidirectional Parallel Peripheral Interface for Personal Computers. Available from IEEE.

  • Hardware


  • Winford Engineering has very handy breadboard adapters and breakout boards with DB-25 connectors.

  • Zanthic has inexpensive proto boards for parallel-port interfacing with EPP handshaking. Some also have a CAN interface.

  • Byte Runner Technologies has parallel-port expansion cards, both ISA and PCI-based.
  • USB Converters

    To connect a parallel-port printer via USB, use a USB/parallel-printer converter, available from many sources.

    To connect a USB printer to a parallel port, see LPT2USB from ePaperSign.

    For other legacy parallel-port applications, see Converter From USB To Parallel from Henrik Haftmann.


    The data sheets for parallel-port controller chips include timing diagrams, register assignments, and other useful details about accessing and using the new modes. PC-side chips are for use in PCs; peripheral-side chips are for use in peripherals.

  • Fairchild's 74VHC161284 Transceiver contains eight bidirectional data buffers and eleven control/status buffers to implement an IEEE-1284 Level 2 interface. Outputs on the cable side can be configured to be either open drain or push-pull.

  • Texas Instruments' TL16PIR552 includes a PC-side ECP+EPP, plus a dual UART and IrDa interface.

  • Cables

  • NFPT (No-Frills Parallel Transfer) includes a DOS program with source code and instructions for building an ECP test cable for transferring files between two PCs using ECP mode. From Kein-Hong Man.

  • Denis Kondakov has figured out how to do Direct Cable Connection ECP transfers between PCs using a simple, home-brewed cable configuration. It requires a patch to paralink.vxd (zip file, 36k).

  • If you want to connect your parallel printer to a USB port, USBGear has a True-Bi Directional USB Printer Cable adapter (USBG-1284Bi) that claims to support bidirectional printer communications. (Most other adapters don't.)

  • Troubleshooting

  • Parallel-port diagnostic and information utility from Parallel Technologies. (88K)

  • PortMon for Windows monitors and displays all serial and parallel port activity on a system. From Mark Russinovich.

  • QualityLogic does printer testing.

  • Connecting Two PCs

    Connecting two PCs via their parallel ports requires a special cable. For software, you can use Windows 95/98's Direct Cable Connection, a third-party product, or write your own program to do the transfers. To find out about Direct Cable Connection, click F1 on the desktop and search for Direct Cable Connection.

  • Sewell Development has data transfer software (FastLynx).

  • Laplink supports PC-to-PC transfers.

  • Also see the information under Cables.

  • About Using Printers

  • Most USB/parallel-port converters are for connecting a parallel-port printer to a PC's USB port. The LPT2USB enables connecting a USB printer to a PC's parallel port. From ePaperSign.

  • Microsoft has printer-related articles:

    HOWTO: Send Raw Data to a Printer Using the Win32 API from Visual Basic. Article ID: 154078.
    HOWTO: Get the Status of a Printer and a Print Job. Article ID: 160129.

  • Do-it-yourself printer repair.

    How to access USB printers using the API functions CreateFile and WriteFile. From Peter Skarpetis.

    Various Projects

    Projects that use the parallel port or an I/O chip like the 8255 Parallel Peripheral Interface chip.

  • PIC 18F4550 Based Project (Parallel to Serial converter). Captures parallel printer port data and redirects it to USB (serial port emulation) using a PIC 18F4550. From Sandro Bureca.

  • How to connect an IDE disk to a microcontroller using an 8255. by Peter Faasse. I've included this one because of many requests for info about IDE interfacing.

  • GKDesign's Universal IR Controller for a PC includes source code and a circuit for reading and sending infrared remote-control signals via the parallel port.

  • World's Least Expensive Pinewood Derby Timer. From James H. Brown.

    Interfacing alphanumeric LCD 16x2 to Parallel Port using VB6. From Erkutlu Science Center.


    There are various ways for applications to access the parallel port and other I/O ports in PCs, including directly accessing port addresses, communicating with a driver that accessing port addresses and using Windows' built-in drivers.

    Under Windows 3.x/95/98/Me, applications can read and write directly to port addresses. Use your compiler's built-in functions (inp and out or similar) or in-line assembly code. (See the source code in my below for an example.) This method is simple, but it's slow, it can't protect the port from access by other applications, and it doesn't work at all under Windows NT/2000/Xp. If you use Visual Basic or another language that doesn't have functions for port I/O or allow in-line assembly code, you can use a DLL or a custom control that adds port I/O functions to an application.

    A system-level device driver enables faster port access and can manage access by multiple applications. Driver types include VxD (virtual device driver) for Windows 9x/Me, WDM for Windows 98/NT/2000/Me/Xp, and kernel-mode driver for Windows NT/2000/Xp. Hardware interrupts must use a system-level driver under Windows 9x/NT/2000/Me/Xp. If you don't want to write your own driver, there are custom controls and other tools that enable applications to access ports and respond to interrupts via a driver.

    A third way to access ports is to use the drivers included with Windows. Windows 3.x/9x/NT have no functions for generic port access, only functions tied to specific uses. For example, there are API calls for accessing printers and for accessing serial ports controlled by UARTs. In Visual Basic, the Printer object and MSComm control are other options for parallel and serial-port access. Built-in functions and controls like these are usually the best solution when their abilities match what you're trying to accomplish.

    Windows 2000/Xp add improved drivers for accessing parallel-port devices with support for SPP, PS/2 (Byte), EPP, and ECP modes and daisy-chaining. Parclass is a system class driver for parallel-port devices, and Parport is a system function driver for the parallel port. The WDK has details. Search for Parallel Devices and Drivers in the documentation index.

    Below are links to tools that you can use for port access. I've grouped them according to which operating systems they're supported in. The list includes freeware, shareware, and commercial products.

    Programming Tools for Port I/O and Interrupts

    For Windows

    InpOut32 and InpOutx64. InpOut32 ported to 64 bits.From Highresolution Enterprises.

  • For testing inpout32.dll in Visual Basic 6, see my example program For testing inpout32.dll in Visual Basic .NET, see my example program

  • I/O Ports Uncensored. How to access ports in C# (CSharp) using inpout32. By Levent S. and the Code Project.
  • Before you can access an I/O port, you need to know its address. The get_io DLL finds port addresses and has been tested in Windows 98/2000/XP. It does not work under Windows NT. (See Jan's FAQ for NT info.) Free. From Graham Bartlett.
  • GetPortAddress is an application that retrieves parallel-port addresses. Free. From Servo Wizard.
  • HOW TO: Access Serial Ports and Parallel Ports by Using Microsoft Visual Basic .NET. How to use WriteFile to access the data port. Knowledge Base article #823179 from Microsoft.
  • Delphi: Accessing Port Hardware and how to use InpOut32.dll. From TK Boyd.
  • IO ActiveX Communications module. Shareware. Line-printer-type access to LPT ports.. From JSPayne.

  • Parallel Port Direct I/O Access package. Shareware. Supports: port I/O. Supports access under NT by changing the I/O permission map for the process that claims the port. From Peter Shoebridge at Zeecube Software

  • RapidDriver generic driver for parallel-port, USB, and other devices. From EnTech Taiwan.
  • TVicHW32 & TVicPort. Shareware. Supports: port I/O and hardware interrupts. From EnTech Taiwan

  • For Windows 95/98/Me Only

  • Freeware. Supports: port I/O. The file contains inpout32.dll, which I wrote in Delphi 2. The zip file includes the DLL, Visual-Basic declarations for inp and out, documentation, a test program, and the Delphi source code, which includes assembly code for port I/O. If you don't see the DLL file after you unzip the files, you probably have system files hidden. To unhide them, go to My Computer > View > Folder Options > View > Hidden Files and select Show All Files. Instructions for using inpout32 with C++ are in Jan's FAQ. To add port access under Windows NT/2000/XP with no changes to application code, see Inpout32.dll above.

  • For Windows NT/2000/Xp Only

  • Direct I/O. Shareware. Incluces interrupt emulation. From Ingenieurbuero Paule.

  • NTPort Library. Shareware. From Zeal SoftStudio.

  • PortTalk. Freeware. From BeyondLogic.

  • 16-bit-only Tools

    Use these with products such as Visual Basic 3 or 16-bit Visual Basic 4 under Windows 3.x.

  • Freeware. Supports: port I/O. Includes an inpout DLL, source code in PowerBasic, and an example VB project. From Lakeview Research.

  • Freeware. Supports: port I/O. Another inpout DLL. Includes assembly-language source code. From Jay Munro.

  • For 16- and 32-bit Programs (Windows 3.x, Windows 95/98)

  • PowerBasic is the source for several products that are useful for applications that access ports. PowerBasic's 16-bit and 32-bit DLL compilers enable you to write and compile DLLs in Basic. The Basic syntax is nearly identical to classic QuickBasic. Because the DLLs are compiled, not interpreted like Visual Basic code, they're fast. The 16-bit edition includes inp and out for port access. The 32-bit edition allows port access under Windows 95/98 via inline assembly code. There's also a 32-bit Basic console compiler for text-only Windows applications and even a DOS compiler.

  • Vbio.dll. Freeware. From Zeal SoftStudio.

  • Other Driver Information and Sources

  • Windows 2000 and Windows Me include a USB printer driver, and the driver can be distributed for use with Windows 98.

  • Linux

  • The ppdev driver enables accessing port bits, interrupts, negotiating, and setting modes.