PC Interfaces and Controlling Devices
- Beyond Logic: Interfacing the PC - collection of PC interfacing documents Rate this link
- HELP PC 2.1 - very large collection of PC hardware programming info in DOS executable hypertext format Rate this link
- Direct I/O port access under Windows95 - Visual-Basic declarations for inp and out, documentation, a test program and the Delphi source code. Rate this link
- 3.5 inch floppy drive power connector Rate this link
- 5.25 - used for harddisks & 5.25" peripherals Rate this link
- ATX Motherboard Power Rate this link
- Background on the ATX power supply Rate this link
- Motherboard Power Connector - AT power supply pinout Rate this link
- PC power supply connectors - AT power supply connector pinout and information Rate this link
- Power Good Signal - how AT power supply "power good"-signal works Rate this link
- Power supply connectors - PC and AT style power supplies Rate this link
- The Windows95 Direct Cable Connect Problem Page Rate this link
- Windows 95 to Windows NT 4.0 Direct Cable Connect Setup Instructions - also between other Windows versions Rate this link
General pinout documents
Power supply connectors
Solving common interfacing problems
- Background Information: Asynchronous Data Transmission Rate this link
- Curt's High Speed Modem Page - modem tips for Windows users Rate this link
- RS-232: Connectors and Cabling - DB-25 pinput. DB-9 pinout, information on RJ-45 wiring and RS-232 port setting in UNIX systems Rate this link
- RS232 Serial Troubleshooting - Due to the flexible nature of the RS-232-C standard, a serial cable can be implemented using hundreds of different pin-to-pin wiring "maps" or diagrams. All these diagrams will work for a given pair of devices, as long as the device signals are handled properly. However, even with a perfect and tested cable you may encounter problems such as garbage data response or no response at all. Such problems are created by other elements of the installation. Rate this link
- RS-232 Tech Bulletin - Make Any Serial Connection Work in 10 Minutes! Rate this link
- Serial communications using TTY protocol - serial port programming, detecting, modifications Rate this link
- Serial ports and Windows 95 - Windows 95 has overturned many of the serial communications barriers of earlier operating systems, however some of its features may not be obvious to many users Rate this link
- Why do I need 16550/16650 UART ? Rate this link
- Wiring a Null Modem cable - Null Modem pin connetion for both 25 and 9 pin RS-232 connectors Rate this link
- Connections Newsletter 2: Serial port powered devices - understanding serial port power capabilities, pdf file Rate this link
- Interfacing the Serial / RS-232 Port - specs, UART pinouts, registers, example software Rate this link
- Technical Data on 16550 - This document is a short description of 16550 UART chip registers. Rate this link
- Diagnosing Serial (Com) Port Problems Rate this link
- Help me find out why my PC doesn't shutdown after I use my modem Rate this link
- How Can I Check My RS-232 Port To Verify Operation? - Perform a "Loopback" test using a Terminal program that lets you Open a serial port to send and receive characters. Rate this link
- C function turns PC into serial-bus master - UARTs built into most microcontrollers support a "9th-bit" communications mode, this function adds this capability to your PC serial port Rate this link
- Implement a nine-data-bit UART on a PC - many microcontrollers , such as the 8051 and the 68HC11, can support a ninth data bit on the asynchronous serial port, UART used in IBM PCs (and clones) does not directly support this operating mode however through some software manipulation, you can add the PC to a serial bus and integrate it into a ninth-bit system Rate this link
- Interfacing the Serial / RS-232 Port - specs, UART pinouts, registers, example software Rate this link
- Laser Transceiver Communicator - This document includes a sample code listing in Borland C++ 3.1 that can be used for full-duplex communication between two computers. Rate this link
- Linux Serial Programming HOWTO - This document describes how to program communications with devices over a serial port on a Linux box. Rate this link
- Serial Communications in Win32 - Serial communications in Microsoft? Win32? is significantly different from serial communications in 16-bit Microsoft Windows?. Those familiar with 16-bit serial communications functions will have to relearn many parts of the system to program serial communications properly. This article will help to accomplish this. Those unfamiliar with serial communications will find this article a helpful foundation for development efforts. This article assumes the reader is familiar with the fundamentals of multiple threading and synchronization in Win32. Rate this link
- Serial Port Central - A collection of files and links to material relating to serial links and networks, especially in monitoring and control applications. This page gives information and communications tools can simplify serial-port programming on PCs. Rate this link
- STP100 Servo Control Manual - This manual has information how to use RS-232 / RS-485 ports with Qbasic. Rate this link
- COM Port Toolkit - COM Port Toolkit is an integrated serial communications testing toolkit. It sends user's data to and receives one from a device and records all transfers to a log. You can test equipment.s serial communications protocol by hand: feed it input, check the output. COM Port Toolkit can capture serial communications between the device and the software by using special serial port driver. So COM Port Toolkit acts as a software protocol analyzer in this mode. COM Port Toolkit works on Windows 95, Windows 98, Windows Me, Windows NT 4.0, Windows 2000/XP operating systems. COM Port Toolkit is available for FREE downloading and using for trial period. Rate this link
- Electronics projects for PC serial port Rate this link
- SIMPLETERM: SIMPle TERMinal Emulator Shareware - a simple shareware tool that can be used to troubleshoot RS-232, RS422 or RS-485 serial communications, runs on DOS, also supports monitor mode which allows SIMPTERM to monitor communications between two other devices Rate this link
- Beyond Logic PC serial port interfacing documents Rate this link
- Devices Powered From RS232 Lines - what to consider when design such things Rate this link
- Serial / RS-232 Interfacing Rate this link
- Serial ports and Windows 95 - article in Rate this link
- UPS serial port monitoring cable Rate this link
Standard PC serial ports come in to versions: 9 pin and 25 pin one. The functions of those both version are exactly the same, only different kind of connectors and different pinout. If you need to convert from one version to other you can do it easily just bu buying a suitable adapter from your local computer shop. PC serial port is nowadays usually used for interfacing your PC to your modem or mouse. Original PC serial port was designed to operate up to 19.2 kbit/s (maximum speed defined in RS-232C standard) but nowadays they can typically go up to 115.2 kbit/s (some special cards can do even faster than that). PC serial port send and receives data in serial format. In serial, asynchronous data transfer the individual bits which comprise each data byte are sent one after the other over a single line. In this context, asynchronous means that the clock information is not included with the transmission, so that frequent re-synchronization using start/stop bits is required. The maximum length specified by RS-232 is only 50 feet (around 15 meters), however much longer lengths are possible with proper shielding on the cable. Generally you can run 9600 bps communication up to 250 feet (80 meters) over shielded data cable or unshielded twisted pair cable in good enviroment. When using shielded cable ans slower data rate longer lengths are possible (up to hundreds of meters in good conditions). The processing element in PC serial port is UART. UART is an integrated circuit used for serial communications, containing a transmitter (parallel-to-serial converter) and a receiver (serial-to-parallel converter), each clocked separately. The parallel side of a UART is connected to computer bus (usually ISA bus). When the computer writes a byte to the UART's transmit data register (TDR), the UART will start to transmit it on the serial line. The UART's status register contains a flag bit which the computer can read to see if the UART is ready to transmit another byte. Another status register bit says whether the UART has received a byte from the serial line, in which case the computer should read it from the receive data register (RDR). If incorrectly formated data is received the UART may signal a "framing error" or "parity error". The UART may be set up to interrupt the computer when data is received or when ready to transmit more data. Data on the serial line is formatted by the UART according to the setting of the UART's control register. Those registers control the baud rate, number of data bits, number of stop bits and what kind of parity is used (odd, even or none).The original UART chip shipped with the IBM personal computer was the 8250. This chip was limited to 9600 bps maximum rate. It was replaced with the 16450 which had the same architecture as the 8250 but has a higher maximum bps specification (115200 bps). Both of the chips only have a one byte FIFO/buffer. The newer 16550 UART contains a 16-byte buffer which helps the computer in the communications and makes faster communication speeds without lost characters possible. A 16-byte FIFO allows up to 16 characters to be received before the computer has to service the interrupt. There are also other UARTs with longer FIFOs. When operating under DOS at speeds below 9600 bps the 16450 should provide satisfactory performance. When operating under any Windows or other multitasking operating system, a 16450 will be limited to about 1200 or 2400 bps reliable communication. 16550 or similar UART will work on multitasking enviroment at high speeds very nicely. Having FIFO in the UART means that the computer need to have interrupts less often, which means less processing power wasted on the serial communications and less likely that data is lost if it takes some time from interrupt request that actual interrupt happens.The UART's serial connections go via separate line driver and line receiver integrated circuits which provide the power and voltages (+12V and -12V) required to drive the serial line and give some protection against noise on the line. If you are purchasing a fast external modem, make sure that the computer's UART can handle the modem's maximum transmission rate. Most modern PC serial cards and built-in serial ports are designed for maximum 115200 bps data rate (please check that you have 16550 or better UART in it). There are also some special serial port card which can handlealso higher data rates (quadruple the clock speed (4X) will allow transmission speeds up to 460,800 bps and a card with 8X setting will allow speeds up to 921,400 bps).
Serial port diagnosing
- Background Information: Printer Interface - Originally designed by Centronics as an interface for their own printers, this interface has rapidly developed into a universally accepted standard throughout the printer world. Rate this link
- 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. Rate this link
- How to build a Laplink and Interlink cables for parallel port file tranfer Rate this link
- Jan's Parallel Port FAQ - hardware interfacing issues to PC parallel port by Jan Axelson, info on problems different parallel port types cause on devices connected to them Rate this link
- Kris Heidenstrom's PC Parallel Port Mini-FAQ - information on the standard and PS/2-bidirectional PC parallel ports, programming examples Rate this link
- Parallel port explained - basics of PC-compatible parallel printer ports Rate this link
- The PC's Parallel Port - FAQ, IEEE1284, software, chips Rate this link
- The typical schematic of original IBM PC parallel port Rate this link
- IEEE 1284 Parallel Port Information Rate this link
- Introduction to the IEEE 1284-1994 parallel port standard Rate this link
- Introduction to the IEEE 1284-1994 Standard - IEEE 1284 is standard that provides for high speed bi-directional communication between the PC and an external peripheral that can communicate 50 to 100 times faster than the original parallel port. It can do this and still be fully backward compatible with all existing parallel port peripherals and printers. Rate this link
- Microsoft's document describing ECP mode - 325k pdf file Rate this link
- A tutorial on Parallel port Interfacing Rate this link
- Beyond Logic PC parallel port interfacing documents Rate this link
- Electronics projects for PC parallel port Rate this link
- External Parallel Port devices and Linux - has also has a lot of technical info on parallel port connected devices Rate this link
- How Inpout32.dll works - The outstanding feature of Inpout32.dll is , it can work with all the windows versions without any modification in user code or the DLL itself. This tutorial describes how it is achieved, what programming methods used, what are the APIs used, etc.... The Dll will check the operating system version when functions are called, and if the operating system is WIN9X, the DLL will use _inp() and _outp functions for reading/writing the parallel port. On the other hand, if the operating system is WIN NT, 2000 or XP, it will install a kernel mode driver and talk to parallel port through that driver. Rate this link
- Interfacing the IBM PC Parallel Printer Port - a good FAQ for anybody interfacing to parallel port Rate this link
- Interfacing to the IBM-PC Parallel Printer Port Rate this link
- Interfacing the Parallel Port - introduction, register usage, example circuits, EPP/ECP Rate this link
- Interfacing the Standard Parallel Port - good tutorial Rate this link
- Logix4u - This site contains programs and tutorials about parallel port and interfacing parallel port. A dynamic link library is available to rectify the problems in parallel port interfacing in WIN NT/2000/XP machines. Rate this link
- Networking with the Printer Port - This article describes internals of Linux PLIP implementation. Rate this link
- Parallel Port Central - links to parallel port documents, Windows DLLs for direct I/O port control Rate this link
- Printer Port interfacing 1 - Schematics for a simple printer port project . Includes code for Visual Basic , QBasic , C and C++. Rate this link
- Parallel Port Page by Juan Carlos Galarza Roca - parallel port programming information Rate this link
- Parallel-printer adapters find new use as instrument interfaces - venerable parallel-printer adapter has found many uses during its long lifetime Rate this link
- UM82C11-C Bidirectional Printer Port Modification Rate this link
- Use of a PC Printer Port for Control and Data Acquisition - A PC printer port is an inexpensive and yet powerful platform for implementing projects dealing with the control of real world peripherals. The printer port provides eight TTL outputs, five inputs and four bidirectional leads and it provides a very simple means to use the PC interrupt structure. Rate this link
- Parallel Port Hardware Properties Rate this link
- Parallel Port Central - Windows DLLs for direct I/O port control from Visual Basic and Delphi, freeware and shareware, links to commerical devellopment tools Rate this link
- Parallel Port Debug Tool - handy DOS utility which gives a visual display of the three software registers used by the Standard Parallel Port Rate this link
- Parallel port monitors - This page has several programs which provide a visual display of the parallel port's status, and which are also able to set the bits one by one. This can be very useful while debugging hardware connected to parallel port and/or its software. Rate this link
- Parallel port monitors - The parallel port is the easiest way to connect a small robotic device or other electronics to a PC. This page gives you several programs which provide a visual display of the parallel port's status, and which are also able to set the bits one by one. This can be very useful while debugging anything connected to parallel port. The software described in this page run on Windows and DOS systems. Rate this link
PC parallel port was originally desingned for connecting your PC to a parallel printer which has Centronics interface. Nowadays the this same port is used for interfacing lots of different kind of peripherals to PCs (scanners, Zip-drives, backup tapes, network adapters). To make the interfacing more efficent the technology has evolved during years. Nowadays paralle port can handle many different operating modes like SPP, ECP and EPP. Parallel port operates by sending all 8 bits of a data byte simultaneously as a ground-referenced TTL level ("parallel") over 8 lines. As soon as the sender has issued the data, he generates a short strobe pulse. The receiver acknowledges processing of the data by sending an "Acknowledge" pulse, thereby confirming readiness to receive new data. In addition to the strobe and acknowledge line, the Centronics interface includes various status lines. Quite high transmission speed (compared to normal serial port) are made possible in the Centronics interface by using simultaneous, parallel transmission of 8 bits. Unfortunately, this advantage comes at the expense of the maximum possible cable length. The assymetrical transmission of many TTL level signals with very steep edges in a cable also means a significant amount of cross-talk. . This problem can be kept to a minimum by using high-quality, twisted-pair cable, whereby each active signal line is connected to a grounded lead in the cable. Practice however has shown that even when using such special cables, reliable transmission cannot be guaranteed under all conditions at cable lengths of over 5m. Maximum cable length for parallel printer cable, when maintaining IEEE-1284 ECP/EPP capabilities, is 31 feet (around 10 meters). The maximum length when there is no need to maintain IEEE-1284 ECP/EPP capabilities depend very much on the quality of the cable when you go boyond that 10 meters. With very heavy well shielded cables and good equipment on the ends parallel data can be transmitted easily tens of meters of distance in SPP mode (Standard Parallel Port mode). Some modern parallel port devices support daisy chaining. The ability to daisy-chain devices is very useful, but if every device does it in a different way it could lead to lots of complications for device driver writers. Fortunately, the IEEE are standardising it in IEEE 1284.3, which covers daisy-chain devices and port multiplexors. Sometimes parallel port is also used for interconenction of 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.
Enhanced parallel port functions
Interfacing to parallel port
Everybody knows what is parallel port, where it can be found, and for what it is being used. the primary use of parallel port is to connect printers to computer and is specifically designed for this purpose. Thus it is often called as printer Port or Centronics port (this name came from a popular printer manufacturing company 'Centronics' who devised some standards for parallel port). Besides interfacing parallel port to printers, it can be used for many other applications quite easily. Parallel port is a simple and inexpensive tool for building computer controlled devices and projects. The simplicity and ease of programming makes parallel port popular in electronics hobbyist world. The parallel port is often used in Computer controlled robots, Atmel/PIC programmers, home automation, etc.
- Infrared Data Association (IrDA) Rate this link
- Introduction to IrDA Rate this link
- Infrared Data Association - IrDA standards Rate this link
- Motherboard IrDA - connector pinout Rate this link
- Motherboard IrDA connector pinout Rate this link
- RS232 to IrDA convertor - pdf document on suitable component for this with example circuit Rate this link
IrDa is an infrared data link standard for short distances. First versio runs uo to 115.2 kbit/s but newer versions can handle speeds up to 4 megabits/s. Many modern PC motherboards have nowadays interface for IrDA module (IR transmitter and receiver). There is some general information on IrDA interface below, including pinouts of IrDA connectors in some motheraboards.
- Don't get burned as USB picks up steam - momentum behind Universal Serial Bus (USB) has picked up steam to the point where buyers are beginning to differentiate PCs based on its presence or absenc Rate this link
- Embedded USB gains ground - With new portable-networking and high-speed options, a growing number of embedded-device designers are adopting the USB for peripheral interface and data transfer. Rate this link
- How USB Ports Work - In this edition of HowStuffWorks, we will look at USB ports from both a user and a technical standpoint. Rate this link
- Linux USB Project Home - This web site was created to serve as a central point of information for USB support under Linux. Rate this link
- Linux USB Frequently Asked Questions Rate this link
- Mini Connector USB Cables: Digital Camera and mp3 player "mini" USB Cables - The new "Mini USB" 4 position connector and new Mini USB "Version 2.0" 5-pin connector are now used on many of the digital cameras coming out today. All of these cables are compatible with all USB versions, USB 2.0, 1.1 and 1.0. In addition to those connectors there has been some non.standard mini connectors on some USB devices. Rate this link
- Understanding Universal Serial Bus (USB) - Good explanation of USB in layman terms. Rate this link
- Understanding USB On-The-Go - USB?s days as a host-centric bus are numbered. USB On-the-Go technology will soon enable USB peripherals to communicate without a host PC. The new capabilities will extend to a raft of consumer products what is already becoming the PC world?s most popular external bus. Rate this link
- Universal Serial Bus (USB) - new fast serial interface bus for peripherals, USB technology forum home page Rate this link
- Universal Serial Bus Links - description, organizations, IC manufacturers, connector specifications, cable and software Rate this link
- Universal Serial Bus Questions and Answers Rate this link
- USB: Adaptable for Industrial Applications? Rate this link
- USB FAQ Rate this link
- USBStuff - company which sells USB equipments and has USBnews on it's web site Rate this link
- USB - Universal Serial Bus - USB connectors pinout reference Rate this link
- An Introduction to USB Development - USB is supplanting old-fashioned parallel and serial interfaces in all sorts of applications. This article will get you well on your way toward including USB support in your product. Rate this link
- Beyond Logic Universal Serial Bus Development Information - Information on USB ICs, pint-to-point connectivity, USB-RS232 interfacing and USB-I2C interfacing. Rate this link
- Buttons for USB HID Devices - USB Human Interface Device Class design information Rate this link
- Hints and kinks for USB decoding - At PC-accessible USB receptacle and at the peripheral receptacle, the USB signal has the format of differential-NRZI (nonreturn-to-zero-inverted) code. After conversion (with a simple circuit or test probes) of this differential to single-ended signal, the signal becomes a waveform that assumes the voltage levels used to recognize ones and zeros in computer code. Rate this link
- Inside USB 2.0: what the new spec means for developers - Is updating to 2.0 worth it? USB-peripheral designers need to know what changes in the spec mean and how the interface handles the challenge of supporting higher data rates while still allowing low- and full-speed devices on the bus. Rate this link
- Taming the Universal Serial Bus - EDN's hands-on USB project gets the bus under control Rate this link
- Texas Instruments USB Specification Rate this link
- Universal Serial Bus Links - description, organizations, IC manufacturers, connector specifications, cable and software Rate this link
- Universal Serial Bus and Game Devices - Universal Serial Bus (USB) is an external PC bus that provides an exciting way to add high-speed game devices to a PC. The Microsoft? DirectInput? application programming interface (API) provides an interface that game developers can use to get fast, consistent direct access to game devices, including USB devices and analog and digital joysticks. This article has general information and links to resources. Rate this link
- Universal Serial Bus Implementers Forum Home Page Rate this link
- USB Central - links to information about USB and sample code to download Rate this link
- USB Designer Links - links to chips, devices, information and software Rate this link
- USB Human Interface Device (HID) Configuration - Information on configuring Linux USB sub-system for USB mouse, keyboard and joystick. Rate this link
- USB Human Interface Device (HID) Related Specifications Rate this link
- Using the HID class eases the job of writing USB device drivers - The difficulty of writing device drivers is one of the major barriers to the adoption of the USB. The USB HID class is a powerful and versatile way to get your device on the USB. If your USB device can exist within the bandwidth limits of the HID driver, then using this driver may save your sanity and your schedule. Rate this link
- USB Specifications and Developer Section Rate this link
- www.usbdeveloper.com - This web page is dedicated to enable electronics enthusiasts or students who may not have the luxury of having a "big company" resources to get information, evaluation boards and support regarding USB and for embedded applications. It provides a lot of hands-on tips to allow you to build a USB systems. This includes application or firmware or architectural fit into systems. Hobbyist guide to USB. Good explanation of USB in layman terms. Firmware for the Philips' PDIUSBD11 USB1.1 chip. Explanation of the USB Bulk-Only Mass storage Class and HID Class. Rate this link
Universal Serial Bus (USB)
The USB is a serial data-transmission system that uses cables to connect peripheral equipment to PCs. All new computers have two or more USB receptacles, and the predictions are that they will replace most of the legacy receptacles on older PCs. The Universal Serial Bus (USB) was born out of the frustration PC users experience trying to connect an incredibly diverse range of peripherals to their computers. It's the child of vendors whose laptops require a small profile peripheral connector. It further promises to reduce the proliferation of cables and wall transformers that overwhelm even the smallest computer installation.
Universal Serial Bus came into life when a group of 7 companies : Compaq, Digital Equipment, IBM, Intel, Microsoft and Northern Telecom decides to form a specifications to merge legacy connectivity such as RS232, Printer port, PS2 port into a single common connector to the Personal Computer. The result : Version 1.0 of the USB specifications delivered on 15 January 1996. Version 1.0 specifies 2 forms of signaling transfer rate : Low Speed (1.5Mbits/sec) and the Full Speed (12Mbits/sec). The motivation of differentiating two transfer speed was to maintain the low-cost implementation of computer peripherals such as keyboards and mice, and, still allow higher speeds devices such that printers and scanners to be able to use the same serial bus. USB was agreed to as a standard by Microsoft, Compaq and many other large names in PC industry. USB 1.0 standard was finally issued in 1996. It was later modified to USB 1.1. Version USB1.1 was delivered on 23 September 1998. The 1.1 specifications clarified many timing parameters which were grey-areas in the past. However, no huge "functional" improvements were given. Like any technology, the start was slow and painful. But after some years it really catched the market. In 27 April 2000, Compaq, Hewlett-Packard, Intel, Lucent, Microsoft, NEC and Philips released version 2.0 of the USB Specifications. While it adds a High Speed physical layer of (480 Mbits/sec), the specifications maintains the Low Speed and Full Speed operation. In effect was a handshake protocol was implemented to negotiate into the different speeds, a new High Speed Hub to manage all 3 speeds and a new Enhanced Host Controller to managed the faster bus and new PIDs to efficiently handle USB bandwidth.
USB is a serial bus standard for interfacing many different kinds peripherals to your PC. It is aimed to replace most of the different kind of special systems of interfacing external devices to serial and parallel port. Most of the new PCs or motherboard have had USB connectors for some time, but the system has not catched mass markests yet because of lack of drivers (Windows 98 has those). USB can power to the devices connected to it. USB can provide plug and play with hot swapping capabilities. USB provides 12 Mbit/s and 1.5 Mbit/s data transmission speeds. USB 2.0 promises even faster speeds up to 480 Mbps. USB 2.0 is backwards compatible so no USB device is rendered out-of-date. A critical part of the philosophy of USB is that users may connect and remove peripherals without powering the entire system down.
USB is a serial protocol and physical link, which transmits all data differentially on a single pair of wires. Another pair provides power to downstream peripherals. USB's topology is a "tiered star". Hubs are the communication nodes that interconnect devices. One, and only one, "host" device (typically a PC) includes the "root hub" which forms the nexus for all device connections. USB system is master-slave tybe bus. The PC is the master that supplied power to the bus and controls the bus operation. The peripheral equipment connected to USB bus just follow the PC controlling. Though USB is physically configured as a tiered star, logically (to the application code) a direct connection exists between the host and each device. Two USB peripherals can't communicate with each other directly, there must always be a master PC in the bus. Two PCs can't be directly wired to each other with USB wire, because there can only be one master in the bus (for PC networking using USB there are USB bridge peripherals that can link two PCs together through their USB ports).
The physical layer were layered with the protocol layer. The protocol layer divides the bus time into several priorities of Control, Interrupt, Bulk and Isochronous transfer. This protocol is handled through a combination of hardware and software on the Personal Computer. The hardware will be the USB Host Controller and the software will most often be Microsoft Windows. The first versio of Windows that supported USB was Microsoft's Windows 95 OSR2.1. USB support became the standard part of Windows 98, and this was the time when the major USB markets started. Later Windows versions have supported USB as well, so USB devices are well supported also on Windows 2000 and XP. Also some non-windows systems support USB hardware. USB support is for example available in new Linux operating system versions. Also new Apple computers have USB ports in them.
The USB standard specifies two kinds of cables and two variations of connectors. High-speed cables, for 12Mbps communication, are better shielded than their less expensive 1.5Mbps counterparts. Each cable has an "A" connector on one end and a "B" on the other. "A" connectors go to the upstream connection while the "B" version attaches downstream. Since the two types are physically different it's impossible to install a cable incorrectly. The standard USB peripheral cable refers to a cable with an A-male connector and a B-male connector. This cable connects on one end (using the A-male connector) to the host computer or hub and on the other end (using the B-male connector) to the device such as printer, scanner, hub, etc. The A-connector and the B-connector are distinct and do not plug into one another. The A-connector is four pin flat connector and the B-connector is a four pin connector that has almost square form (just two corners rounded). Ready made USB cables are available in a wide variety of length ranging from .5 meters to 5 meters. 5 meters (about 15') is the maximum cable length allowed by the USB specification. USB maximum cable distance is 16 feet. USB hubs cab be used as repeaters when longer distancs are needed (there is a limitation that you can't have more than few USB HUBs in series though).
USB cable lengths are limited to 5m for 12Mbps connections and 3m for 1.5Mbps. This sounds backwards, but stems from the use of better cables at higher speeds. Five meters is the maximum cable length allowed by the USB specification. You can achieve longer cable runs by inserting a hub every five meters. Alternatively you can chain Active Extension cables to attain the needed distance. If you need longer distances you need to connect many 5 meter segments after each other. Other alternative is to use an "Active Extension Cable", which is basically a 5 meter cable with a built in 1-port hub. You can chain maximum four of these plus a single 5 meter USB peripheral cable to give you the 25 meter maximum reach.
It may seem like an A-male to A-male cable would be handy to connect two USB hosts together. DO NOT DO THIS! This will short out your computers, possibly causing serious damage. USB was not designed to work this way. USB can't be used directly as a fast connection between PCs, but here are special products which allow small scale networking using USB bus (USB Host to USB Host Adapter). To connect two computers together you will need a USB bridge, a USB Peer to Peer cable for file and hardware sharing or a USB Data Transfer Cable for file sharing.
In best case USB interface is a very well working plug & play bus if the devices have built-in drivers in the operating system orthe manufacturer gives you good drivers. But for do-it-your self people USB is not the friendliest environment to work with. First the USB itself is quite complicated to implement and second problem are the drivers. For building your own USB peripherals you need to conform to a generic USB driver class, such as Human Input Device class, Mass storage class, etc. or you need to write a WDM driver for yourself - not easy.
The USB interface uses four pin connector (two different connector forms, known as A and B).?Two pins carry the data (in differential bidirectional bus) and two other pins carry operating power for devices (+5V and ground, current rating 100mA or 500mA depending on device). Though nominally +5V, the spec allows for quite a bit of variation in this; designers should allow for as little as about 4V. A peripheral that draws up to 100 mA can extract all of its power from the bus wiring all of the time. Higher current requirements are trickier; if the device requires less than 500 mS, and if the upstream host or hub can provide that much power (which is optional), the device can be bus-powered if at power-up time, during system configuration, it consumes less than 100 mA. If the device needs more than a half-amp, then it must have its own power supply. USB system has power managing built in. USB hosts and hubs manage power by enabling and disabling power to individual devices to electrically remove ill-behaved peripherals from the system. Further, they can instruct devices to enter the suspend state, which reduces maximum power consumption to 500 microamps (for low-power, 1.5Mbps peripherals) or 2.5 mA for 12Mbps devices.
The USB specification recognizes two kinds of peripherals: stand-alone (single function units, like a mouse) or compound devices (those that have more than one peripheral sharing a USB port). An example of a compound device is a video camera with separate audio processor. Hubs are bridges; they increase the logical and physical fan-out of the network. A hub has a single upstream connection (that going to the root hub, or the next hub closer to the root), and one to many downstream connections. Hubs are themselves USB devices, and may incorporate some amount of intelligence. Though physically configured as a tiered star, logically (to the application code) a direct connection exists between the host and each device.
The USB standard defines four data transfer types: control, isochronous, interrupt, and bulk. All USB peripherals must support the control transfer type for configuration, command, and status information. Each of the remaining three data transfer types targets a particular category of USB peripheral. The bulk transfer type targets USB devices such as printers, scanners, and digital cameras that move large amounts of data to or from the PC over USB.
USB cables utilize two specially designed 4-pin plugs and receptacles. The "upstream" plug is called "A" and the "downstream" plug is called "B". This format is intended to minimize end user termination problems, thereby ensuring proper connectivity. Use the A connector to connect with a host or downstream connection on a hub. Use the B connector to connect to the peripheral appliance. The USB cable consists of one twisted pair for data and two untwisted wires for powering downstream appliances. Specifically, a full-speed cable contains a 28-gauge twisted pair, an untwisted pair of 28 to 20 gauge power conductors, an aluminized polyester shield, a drain wire, and an overall 65% (minimum) copper braid. Nominal impedance for the data pair is 90 ohms. The maximum cable length for USB is a function of signal propagation delay. The cable may have no more than 26 nS delay from connector A to connector B. An additional allowance of 4 nS is split between the sending device connection and the receiver connection/response function, making the entire one-way delay 30 nS maximum. In addition, the cable may not have a velocity of propagation greater than 5.2 nS per meter. The length and twist of the data pair must be matched well enough so that no more than 0.10 nS time skew exists between bit polarities. The nominal differential signal level is 800 mV. The Implementers Forum says that fully compliant USB 1.1 cables will perform at USB 2.0 speeds. The maximum USB cable length according the standard is 5 meters. With the maximum of 5 hubs connected with 5m cables and a 5m cable going to your full speed device, this will give you 30m of cable between your device and PC.
The 1.0 and 1.1 standards for USB were for 1.5 and 12 Mbps at low- and full-speed rates, respectively. The latest 2.0 standard is for a 480-Mbps rate that will accommodate many high-speed devices along with the previous low- and full-speed rates. The naming of USB has confused since then. Customers were asking what version USB was installed on a machine and if it was USB 1.1 they thought it inferior to USB 2. In December 2002 USB Forum announced that henceforth USB 1.1 would be called USB 2 and USB 2 would continue to be called USB 2. To help the public grasp this subtle distinction USB 2, which was the old USB 1.1, would have ``Full Speed'' added to its title and USB 2, which was USB 2, would have ``Hi-Speed'' added. So nowadays USB 2 could be USB 1.1 or USB 2 depending. This has confised the market and customers. Now www.usb.org says that: ``The correct nomenclature for high-speed USB products is ``Hi-Speed USB.'' The correct nomenclature for low or Full-speed USB products is simply ``USB''. And in the FAQ section it states: ``High speed USB products have a design data rate of 480 Mb/s. Full speed USB devices signal at 12Mb/s.'' On some texts those two different maximum speed USB versions are referred as OHCI and EHCI. OHCI refers to 12 Mbps USB version and EHCI refers to 480Mbps USB version.
USB device design and driver information
USB is a complex standard that requires an enormous amount of software support, both on the firmware side and in the host computer. Most host-end connections, for better or worse, will be PCs running a Microsoft operating system. USB is not supported at all in DOS, Windows 3.x, or Windows NT. Windows 95 provided some USB drivers, though only in the later versions starting with OEM Software Release 2.1. All Windows 98 releases include a full set of drivers for common USB applications. Windows 2000 and XP has this same USB support too. A USB driver is a difficult beast. The good news is that in many cases the drivers provided with Windows will handle even your custom peripheral. Windows, as well as the USB specification, segments drivers into "classes," where hardware that falls into a single class shares similar interfaces. A class defines a baseline specification for a given set of capabilities; all devices in a class require comparable types of software support. An example is the human interface device (HID) class, which supports devices like mice, joysticks, and keyboards. Another is the monitor class, which controls image position, size, and alignment on video displays. Custom drivers are an alternative to class drivers. A custom driver exploits the capabilities of a particular piece of hardware at the end of the USB cable. Unless you're building a typically PC-centric peripheral like a mouse, you'll likely also create a host application that exchanges data with the USB device and interacts with the user. To exchange data with the USB device the application code simply issues standard file-like API calls, using a standard Windows handle to identify the device. Since USB is (for all practical purposes) tied to the high-volume PC business, dozens of vendors offer hundreds of different support chips. USB parts are rather hard to categorize, but fall generally into three camps: host-side USB controllers (which live inside the PC, and are probably of little interest to ESP readers), devices designed as stand-alone USB peripheral controllers (like a smart UART, these chips handle communications but you'll need another microprocessor as the brains of your device), and versions of popular processors that include a USB interface. Beyond these three categories, some vendors offer specialized parts, such as USB camera controllers, audio devices, bridges that link USB to other buses, and specialized HID controllers. Development tools are as important as chips and code. USB is a complex protocol that tosses a lot of data around. Debugging by looking at the serial stream on a scope is not efficient. Several companies offer protocol analyzers that monitor the USB link and display transmitted data in an understandable form.The USB sponsoring organization has created a compliance program to ensure that devices meet the standard's specifications. Though no law mandates that any device must pass these tests, doing so ensures that the user's experience with your products will be as trouble-free as possible.
- 1394 Trade Association Rate this link
- Designing 1394b technology into next-generation electronic systems - Enhancements to 1394b promise to extend 1394 connectivity to more applications. The 1394b specification is a significant enhancement that enables speed increases to 3.2 Gbps; supports distances of 100m on UTP-5 (unshielded twisted pair Category 5), POF (plastic optical fiber), and GOF (glass optical fiber); and significantly reduces latency times by using arbitration pipelining. The standard is backward-compatible with the current 1394-1995 and 1394a specifications. With its long-haul capabilities, 1394b makes 1394 the convergence bus between PC products, consumer-entertainment systems, and home networking. Rate this link
- EDN hands-on project: Firewire unleashes the power of digital video - IEEE-1394, or Firewire, serial bus promises to enable a number of new applications that rely on rich, high-speed data streams, such as digital video Rate this link
- Fire on the Wire: The IEEE 1934 High Performance Serial Bus - The IEEE 1394-1995 standard for the High Performance Serial Bus, here abbreviated to 1394, defines a serial data transfer protocol and interconnection system that "provides the same services as modern IEEE-standard parallel busses, but at a much lower cost." 1394 incorporates quite advanced technology, but it's the "much lower cost" feature that assures 1394's adoption for the digital video and audio consumer markets of 1997 and beyond. The capabilities of the 1394 bus are sufficient to support a variety of high-end digital audio/video applications, such as consumer audio/video device control and signal routing, home networking, nonlinear DV editing, and 32-channel (or more) digital audio mixing. Rate this link
- FireWireStuff - basic information and product links Rate this link
- Guideline of Transmission and Control for DVD-Video/Audio through IEEE1394 Bus Rate this link
- IEEE 1394 drives expand video-storage options - Consumer-electronics manufacturers are considering IEEE 1394 disk drives to solve the cost, upgrade, and reliability problems with today's embedded approach to digital-media storage. Rate this link
- IEEE 1394 Connector Pinout Rate this link
- IEEE 1394 Technical Introduction Rate this link
- Texas Instruments IEEE 1394 High Performance Serial Bus Pages Rate this link
- The Challenges of 1394 PHY Design Rate this link
- The Firewire Connection - magazine article about IEEE 1394 Rate this link
IEEE 1394 is a fast serial bus which is a little bit similar to USB but is capable of much higher speeds (up to 400 Mbit/s). In terms of configuration and how it is used in the PC however, IEEE-1394 can be thought of as "USB, only faster". It is a serial interface that supports dozens of daisy-chained devices, hot-swapping, and plug-and-play. However, instead of USB's 12 Mbits/second maximum transfer rate, IEEE-1394 supports up to 400 Mbits/second.
The IEEE 1394 standard defines both a backplane physical layer and point-to-point cable-connected virtual bus implementations in terms of media, topology, and protocol. The cable version of the IEEE 1394 standard supports data rates of 100, 200, and 400 Mbps (half duplex operation). The 1394a-2000 standard provided functional enhancements to 1394-1995 to increase 1394 bus throughput at the same data rates. IEEE 1394b specification added 800Mbits/sec speed and full-duplex operation. The typical media used to carry the data signals is two individually shielded 110 ohm twisted pairs (for example 28-30 awg 110 ohm). In addition to that many cables have somewhat thicker wires for carrying power (for example two 22-28 awg lines). he 1394 specification limits cable length to 4.5 meters.
IEEE 1394 is designed to operate as peer to peer network meaning that there is no different master and slave devices (all IEEE 1394 port are the same). Devices on the bus are Hot-Swappable. The digital interface supports either asynchronous and isochronous data transfers. Addressing is used to a particular device on the bus. Each device determines its own address. IEEE 1394 supports up to 63 devices at a maximum cable distance between devices of 4.5 meters. However, "powered" Firewire devices and repeaters will repeat a signal and allow you to extend another 15 feet. The maximum devices on the bus is 16 allowing a total maximum cable distance of 72 meters. The 1394 specification limits cable length to 4.5 meters in order to satisfy the round trip time maximum required by the arbitration protocol. Some applications may run longer lengths when the data rate is lowered to the 100 Mbps level.
The 1394 system utilizes two shielded twisted pairs (110 ohms) and two single wires. The twisted pairs handle differential data and strobe (assists in clock regeneration) while the separate wires provide power and ground for remote devices needing power support. Signal level is 265 mV differential into 110 ohms. The 1394 specification provides electrical performance requirements, which leave open the actual parameters of the cable design. As with all differential signaling systems, pair-to-pair data skew is critical (less than 0.40 nanoseconds). Crosstalk must be maintained below -26 dB from 1 to 500 MHz. The only requirement on the size of wire used is that velocity of propagation must not exceed 5.05 nS/meter. The typical cable has 28 gauge copper twisted pairs and 22 gauge wires for power and ground. A Firewire connected appliance may or may not need power from its host, but must be capable of providing limited power for downstream devices.
The 1394 specification supports two plug configurations: a four-pin version and a six-pin version. Six-pin versions can carry all six connections and are capable of providing power to appliances that need it. For independently powered appliances, like camcorders, the four-pin version is used for its compactness. Cable assemblies have the data signal pairs crossed over to avoid polarity issues. All 1394 type appliances have receptacles, which makes for easy upstream-downstream connection with the male-to-male cable.
New standard version have increased the avaialble media from original short "Firewire" cable to other medias also. Transmitting data over CAT5 cable allows data at 100Mbps to travel 100m (specified in IEEE 1394b). Fiber cable will allow 100 meter distances at any speed (maximum speed depends on the type of fiber cable).
IEEE 1394 is nowadays used for interconnecting modern digital video equipments, like for example DV video camera, to a PC. Allows live connection/disconnection. IEEE 1394 was called Firewire before standardization in IEEE. IEEE-1394 is also defined as part of the SCSI-3 family of related standards, and was at one point sometimes called "serial SCSI". In reality, though, IEEE-1394 still has not taken off as a storage interface within the PC. IEEE-1394 does continue to grow in popularity in a variety of specialty markets, especially digital video, where it may well become the next big interfacing standard for consumer electronics devices like camcorders and VCRs. In PC accessories world, the future of IEE 1394 is somewhat uncertain, and the creation of the new, faster USB 2.0 standard continues to keep the waters cloudy. But when we are talking on video applications, IEEE 1394 continues to be the preferred interface over USB.
IEEE 1395 and Ethernet technologies are converging in some sense. The 1394 Trade Association is working with the IEEE (Institute of Electrical and Electronics Engineers) to develop a combined Ethernet/1394b PHY (physical layer). Once put into silicon, this PHY would live inside a hub that would connect all endpoints in a network regardless of what protocol those endpoints wanted to employ. That is, 1394 devices would think they were on a 1394 network, and Ethernet devices would think they were on a standard Ethernet network. At some point in the network, a bridge would allow Ethernet traffic to cross over to the 1394 "side" and vice versa. Instead of having to worry about differing network technologies, users would see a single RJ-45 wall jack that would simply work with whatever device they chose to plug into it. Inside the walls, an infrastructure of category-5 cable would carry both Ethernet and 1394 traffic. The key to the effort is an autonegotiation protocol that would allow each port to select from various link-layer protocols, including 10- and 100-Mbit/sec Ethernet, 100-Mbit/sec 1394b, Gigabit Ethernet, and 400- or 800-Mbit/sec 1394.
- Beyond Logic AT keyboard interfacing documents Rate this link
- Interfacing the PC's keyboard - how it works and how to decode PC keyboard signal using microcontroller Rate this link
- Interfacing the AT keyboard - Why would you want to interface the Keyboard? The IBM keyboard can be a cheap alternative to a keyboard on a Microprocessor development system. Or maybe you want a remote terminal, just couple it with a LCD Module. Rate this link
- Electronics projects for PC keyboard port Rate this link
- Help with IBM-PC keyboard interfacing Rate this link
- Interfacing the AT Keyboard Rate this link
- IBM-PC keyboard interfacing Rate this link
- PC Keyboard FAQ Rate this link
- PC Keyboard Scan Codes - The PC keyboard interface is designed so the system software has maximum flexibility in defining certain keyboard operations. This is accomplished by having the keyboard return scancodes rather than ASCII codes. Each key generates a 'make' scancode when pressed and a 'break' scancode when released. The computer system interprets the scancodes to determine what operation it is to perform. For historical compatibility reasons computers can employ different sets of scancodes for different purposes. Rate this link
- PS/2 Keyboard & Mouse Protocols - Auxiliary Device and System Timings Rate this link
- PS/2 Mouse/Keyboard Protocol Rate this link
- PS/2 Mouse/Keyboard Protocol - This article describes the protocol and shows how to implement it using PIC 16F84. Rate this link
- The PC's keyboard - interfacing tutorial Rate this link
- USB Human Interface Device (HID) Configuration - Information on configuring Linux USB sub-system for USB mouse, keyboard and joystick. Rate this link
- What is a Keyboard Wedge? - A keyboard wedge is a system whereby it becomes possible to enter data into a computer in a way not anticipated by the programmer who wrote the application. It is based on the idea that all applications programs allow data to be entered via the keyboard. If the computer can be fooled into accepting 'dummy' keyboard data then that data will be processed and handled correctly by the application. Wedge systems are typically used to enter small packets of machine collected data into applications written for keyed data. This data may come from a barcode reader or similar device. Rate this link
- PIC - PS/2 mouse interfacing and communication - contains PC mouse protocol information and some examples how to interface it using PIC microcontroller Rate this link
- PC mouse information - This documents tries to tell how PC mouse hardware works and how to read it at the lowest level. This document contains information on serial port mouuse protocols including Mouse Systems, Microsoft and Logitech protocols. Document contains also some information on PS/2 and bus mouses. Rate this link
- PS/2 Mouse/Keyboard Protocol - This article describes the protocol and shows how to implement it using PIC 16F84. Rate this link
- The PS/2 Mouse Interface - This document is a good description of PS/2 mouse protocol. This describes the basic PS/2 mouse and wheelmouse protocols. Rate this link
- Active PS/2 Muxing - defines a method for attaching up to four PS/2 pointing devices to a PC, pdf document Rate this link
- PC mouse adapters - is it possible to convert PS/2 mouse to serial port or the other way Rate this link
- PC mouse hardware and protocols - microsoft, mouse system, bus, PS/2 Rate this link
- PS/2 Mouse/Keyboard Protocol Rate this link
- Build Your Own Arcade Controls - Inside this site, you will find a variety of alternatives for controlling games on your computer. Imagine playing PacMan using a real ball-top arcade joystick, or Robotron with dual arcade sticks. Imagine Tempest with a real arcade spinner. Imagine playing the old Atari 2600 games using a real Atari 2600 joystick. Imagine using arcade controls on games that don't even support a joystick. It's all inside here. Rate this link
- Build Your Own Cockpit - collection of articles dealing with building your own cockpit, rudders, and any other stuff to enhance your computer simulation experience Rate this link
- Electronics projects for PC joystick port Rate this link
- Wheels and Pedals - how to build your own Rate this link
If you're typing on a standard QWERTY keyboard, and most of us are, then your keyboard design is over 100 years old (135 years old). Just about every computer comes factory equipped with a standard flat QWERTY keyboard. New and innovative designs for keyboards have been developed over the past few years. Traditional PC keyboard connects to a PS/2 kayboard interface (6 pin mini DIN connector) on the PC motherboard (some older PCs used 5-pin AT type interface which is electrically practically the same, but just different connector). The keyboard interface actually uses four wires.The IBM keyboard you most probably have sitting in front of you, sends scan codes to your computer. The scan codes tell your Keyboard Bios, what keys you have pressed or released. Besides Scan codes, commands can also be sent to and from the keyboard. PC's keyboard implements a bi-directional protocol. The keyboard can send data to the Host and the Host can send data to the Keyboard. The communication between keyboard and PC moherboard is handled by a special keybaord interface controller IC. Traditional PC motherboard expects that there is a keyboard connected to it when the system boots up. The PC BIOS hardware check routines will check if the keyboard exist, and generally give an error when no keyboard is attached. This generally means that you can't boot a PC normally without a keybord installed to it. If you need to boot up a computer without a keyboard, check your computer BIOS settings. There should be settings in your BIOS set up to skip the keyboard check, this allowing the PC to boot without a keyboard. The PC keyboard interface is designed so the system software has maximum flexibility in defining certain keyboard operations. This is accomplished by having the keyboard return scancodes rather than ASCII codes. Each key generates a 'make' scancode when pressed and a 'break' scancode when released. The computer system interprets the scancodes to determine what operation it is to perform. For historical compatibility reasons computers can employ different sets of scancodes for different purposes. The newest PC keybord products are the ones that connect to USB bus. This does not immediatly replace the traditional PC keyboard, but could be a nice oftopn of extra special keyboard for computer is needed. USB keyboards belong to USB Human Interface Device (HID) class.You may not need any operating system support at all to use a USB keyboard if you have a PC architecture. There are several BIOS available where the BIOS can provide USB support from a keyboard plugged into the root hub on the motherboard. This may or may not work through other hubs and does not normally work with add-in boards, so you might want to add in support anyway.
PC mouse is the most commonly used pointing device for operating graphical user interface (GUI) of the operating system and software running in it. Nowadays there are different techniquest used on mouse to detect themovement and sending that information to computer. For optomechanical designs, a ball makes contact with the desktop surface and rotates two rollers, positioned 90? from each other, as the mouse moves. As each roller moves, it spins a disc with evenly spaced holes along its outer edge. An infrared sensor sees light pulses from the infrared LED on the other side of the disc as the holes pass in front of the sensor. The mouse has two sets of infrared LEDs and sensors for each disc. Counting the pulses and applying acceleration and trajectory heuristics, determines how the mouse movement translates into cursor movement. Optical mouse implementations bounced light off a a surface. Early optical mouse implementations used a special mouse pad thathad a grid of dark lines that interrupted the beam of light when the mouse moved, allowing the software to track the mouse movement. Usually the X and Y direction lines in grid are made with different color, so an optical sensor designed different wavelength can can separate X and Y lines.Contemporary optical mice do not require a mouse pad and can work on almost any surface. Optical mice reflect the light from a red LED and sample it with a CMOS image sensor (as many as 1500 times per second). A special DSP chip performs signal processing on each sample image to detect patterns in the desktop surface and to determine how those patterns have shifted since the mouse took the previous sample. This pattern movements determines the direction and amount of mouse movement.There is wide variety of different PC mouse types. The first mouse productsconnected to PC serial port. The first and nots common serial port mouse types were Microsoft Mouse and Mouse Systems mouse. Both of them used 1200 bps serial communication between mouse and PC, but used different data formats. Those were long the major mouse protocol types (later there were some variations of those with higher data rate and more buttons support, mostly used by Logitech). The next mouse type and most common nowadays is a PS/2 mouse. It was introduced by IBM long time on their IBM PS/2 range of computers. Later other PC manufacturers adopted this mouse port type ot their motherboards. PS/2 mouse uses same type of connector as PS/2 keyboard (6 pin mini-din) and a base data protocol quite similar to PS/2 keyboard (altough different data packets). Modern ATX format PC motherboards have PS/2 mouse port by default, so this is the mouse type you propably got with your new computer. The PS/2 mouse uses the same protocol as the PS/2 (AT) keyboard, but just send different codes than keyboard The standard PS/2 mouse supports the following inputs: X (right/left) movement, Y (up/down) movement, left button, middle button, and right button. The mouse reads these inputs at a regular freqency and updates various counters and flags to reflect movement and button states. There are many PS/2 pointing devices that have additional inputs and may report data differently than the "Basic PS/2 mouse". The latest new series of products are mouse products which conenct to USB bus. Those USB mouse products belong USB Human Interface Device (HID) and use this series of standard drivers (or special drivers supplied by mouse manufacturer). The different pc mouse types in use are incompatible with each other. They use different electrical interfaces and data formats. There are some mouse products on the market which support more than one mouse protocol / interface at the same device. At those case those mouse products are supplied with a connector adapter which adapts the connector model and pinout form one port to another. Those mouse products supplied with the adapters are designed in such way that they work differently depending if the adapter is plugged in or not (so they always work according the interface specification in use). I have seen adapter for example for serial-PS/2 and PS/2-USB interfacing. Those adapters work nicely with the mouse they are supplied with, but they are not interchangeable with any mouse (they work only with "dual mode" mouse which supports both protocol). Those adapters are not suitable for any other use and do not work with any generic mouse. The mouse needs a mouse driver to work (a right driver type for mouse type you use). The mouse driver in the computer received that data packet and decodes the information from it and does actions based on the information. Typically mouse driver has the information of the current mouse state (position and button states) and tells them to the application or operating when it asks them. Typically the mouse drive calls mouse cursor moving routines when mouse is moved and sends messages to the software when buttons are pressed. In typical modern PC mouse driver the actual cursor movement is not linearly related to the mouse movement. This might sound a bit strange but it has been found that there are better ways to change the mouse movement to cursor muvement than just simply causing one mouse step to move the cursor one pixel. During the pioneering research done at Apple Computer in the devellopment of the graphical user interface (GUI), it became apparent that no particular ratio between mouse movement and cursor movement was best suited for all tasks.
General mouse information
Solving mouse problems
Mouse specific hardware information
From the start of PC era, the most common PC joystick type is PC analogue joystick. This joystick model was presented by IBM together with their first IBM PC computer. The joystick is just a basic analogue joystick with two buttons (many newer joystick have added more buttons and controls though). A basic anlogue PC joystick consists of two potentiometers with variable resistance value between 0 Ohm and 100 kohm plus two buttons wired to right 15 pin joystick connector pins. Most PC soundcards nowadays have this 15 pin joystick interface in them (those soundcards generally have both MIDI and joystick functions on some connector, which causes sometimes problems). Original joystick interface had circuit for connecting two joysticks, but had only one joystick connector. The joystick interface card was designed to be as simple and cheap as possible, which caused that part of the analogue/digital conversion sampling process need to be done with software (in practice a pulse width measurement). This has caused anormous amounts of problems to game programmers when computers have become faster and faster all the time (drivers were need to be updated often earlier). Nowadays analogue joystick drivers work, but have pretty much processor overheard because of the "stupid" design. Traditional PC stering wheels, pedals and gamepads generally use the same interface ideas as the original PC joystick. There have been for quite long time so called "digital joysticks" available for PC joystick interface (which is designed for analogue joysticks).Digital joysticks are all different and use proprietary communicationmethods. They work generally only with Windows (do not work with classic DOS games). The computer can only detect thedigital joystick properly if the correct driver is installed. Driverscan be downloaded free from manufacturer's websites in most cases. Some modern joystick have build to have two operation modes: analog and digital interface. Some digital sticks (like the MS Sidewinder 3D Pro) will work inanalog mode by setting a switch to a certain position, but of coursein this case only the basic functions can be supported (extra buttonsand axes will not work).In analog emulation it emulates the two resistors in a standard joystick. The other mode is all digital where it sends a serial data stream on one of the joystick button inputs, It feeds a clock on another of the button inputs. Those digital signals are then interpreted on some special joystick driver. Some joystick even don't support the traditional analogue interface (just their proprietaty digital communication protocol which their driver understands). The newest joystick type on PC joystick market are the USB joysticks. USB joystics are joysticks which connect to USB bus and use digital communication. USB joysticks belong to USB Human Interface Device (HID) class.
Solving common joystick problems
Build your own
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