Serial and parallel ports, their purpose. Serial and parallel I/O ports
The parallel port (LPT for short) appeared on the very first IBM PC. Sometimes it is called Centronics - after the name of the development company. The parallel port was previously used primarily to connect printers.
Modern printers usually connect to a computer via USB (see Chapter 10), but many models have a connector for connecting an LPT cable (parallel port cable).
Let's learn how to find parallel port connectors. In Fig. Figure 9.1 shows the LPT connector on the Lexmark E321 printer - a fairly modern model (the printer was purchased last year). Below it is a USB connector with a connected USB cable. This indicates that the printer is currently connected to the computer via USB.
Rice. 9.1. LPT connector on the printer
If the printer was connected to a parallel port on a computer, then we would need the cable shown in Fig. 9.2.
Rice. 9.2. Cable
In Fig. Figure 9.3 shows the motherboard. The largest connector shown in this figure is the parallel port. It is usually colored pink to connect devices to the computer's parallel port. How to distinguish between serial and parallel ports, which are the same size? The parallel port connector is female and the serial port is male. In other words, even if you mix up the colors (the serial port is usually blue), you will not be able to connect to the serial port using an LPT cable.
Rice. 9.3. Parallel and serial ports
In addition to a printer, you can connect to the parallel port:
Some storage media, for example external CD-ROM drives, magnetic drives of “increased” capacity (previously 120 MB was considered increased capacity);
Tape drives are data storage devices on magnetic tape. Nowadays they are practically not used, but previously they were often used to create backup copies on enterprise servers - after all, magnetic tape cost a penny compared to other storage media and made it possible to record large volumes of information at that time (several gigabytes);
Old-style scanners (modern ones are connected via USB).
Frankly, I doubt you'll need to use a parallel port today, but it's a possibility - maybe you have an old printer that still works well, but only connects to an LPT port. Then you should know about the operating modes of the parallel port (the operating mode of the port is usually selected in the BIOS):
SPP (Standard Parallel Port) – standard parallel port mode. This mode allows only one-way data transfer from the computer to the peripheral device connected to the port. Data transfer rate – 200 Kbps;
EPP (Enhanced Parallel Port) – advanced mode. Two-way data exchange is allowed. Operation speed – up to 2 Mbit/s. Connection of up to 64 peripheral devices is allowed (in a chain);
Terminal. Immediately after the first launch, the program will ask you if you want to make Hyper Terminal Telnet the default application. You can answer her Yes and continue working. In the next program window, you will need to give the connection a name and select an icon for it.Now you are taken to the program window, where you will be asked to select a connection method (in our case, this will be the name of the modem, Fig. 6.31) and enter the phone number to connect to.
Rice. 6.31.
All Bluetooth devices are at risk of attack. The main recommendation that can be applied to prevent such attacks is to not enable Bluetooth device discovery unnecessarily. However, even following this advice will not save you from risk.
Let's look at some Bluetooth attacks and how to protect against them. In table 6.1 (data from the sites www.trifinity.org and www.bluejack.ru were used to construct the table) provides information about attacks and methods of protecting against them.
It should be noted that Bluetooth attacks are possible at a short distance - usually 10-15 meters, although the possibility of using directional antennas increases this distance.
| Protection against Bluetooth attacks | Attack name | Description |
|---|---|---|
| Methods of protection | BlueBug | Owners of old mobile phones should replace the firmware with a newer one, owners of all devices should reject suspicious connection requests, enable Bluetooth connection protection, turn off Bluetooth when it is not needed |
| BlueSmack | Various BT devices can be attacked. This is a DOS (Denial of Service) attack. denial of service). A device susceptible to attack immediately “falls” - hangs, or reboots. | hardware address device with which the device has already communicated.Software methods There is no protection yet; the only thing that can be recommended is to turn off Bluetooth when it is not needed. |
| CarWhisperer | Car sound systems equipped with Bluetooth may be attacked. The attack is based on guessing the access code to the device, after which the attacker can use it. | Change the factory access code for the device. |
| BlueChop | An attack aimed at destroying piconets. | Perhaps the most effective method of combating this attack is to search for an attacker who is located nearby (tens of meters) from your piconet. |
| BlueBump | An attack based on social engineering methods. First, the attacker legally connects to the victim's device by sending him a business card and a connection request, after which the connection can be deleted, and the attacker creates an additional connection, until which he can freely connect to the device. | Do not accept suspicious connection requests |
| HeloMoto | An attack on Motorola phones that can be thought of as a combination of the BlueBug and BlueSnarf attacks. | Features of the Bluetooth implementation in Motorola phones are that the devices are discoverable within 60 seconds after activating the interface. If the attacker did not catch you within these 60 seconds, then you do not have to worry about this attack. |
Having talked about Bluetooth security, let's discuss network problems.
The transfer of data from the central processor to any peripheral device and vice versa is controlled by setting an interrupt request IRQ...
Interrupts and addresses
The transfer of data from the central processor to any peripheral device and vice versa is controlled by setting an interrupt request (IRQ) and an I/O address. For an external peripheral device, the interrupt request and I/O address are assigned to the port through which it is connected.
The very words “interrupt request” indicate that the CPU is being interrupted and is being instructed to deal with data coming from some device. There are 16 interrupts in total - from 0 to 15. All serial and parallel ports generally require their own interrupt request, except that COM1 and COM3, as well as COM2 and COM4, often have a common interrupt request.
For each port, you need to specify a unique I/O address, which is similar to a mailbox for correspondence arriving at the CPU address, in which it is stored until processed. If any interrupt request or I/O address is used by more than one device at the same time, then none of them will work properly and may even freeze the PC.
If there are problems with a port, check which interrupt requests and I/O address are assigned to it.
Control panel - System - Devices - COM and LPT ports
If you see a yellow circle with an exclamation point inside before any line, you may find the cause of the “interference”. With the line highlighted, click "Properties - Resources". In the "List of conflicting devices" field, find what is causing the conflict. If it turns out that it is some old board that does not support Plug & Play, it will be listed as an “Unknown Device”.
To resolve the problem, change the interrupt request or I/O address for one of the offending devices. If the port is on the system board, use the System Setup (BIOS) program to do this.
To enter System Setup during PC startup, press the “Delete”, “F1” or other key - find out in the system documentation. In many setup programs, you can assign an interrupt request and an I/O address (set resources) to each specific port, overriding the old ones.
Find an unused interrupt request or I/O address.
Control Panel - System - Devices - Computer
You will see a complete list of applied resources. If there are no unused interrupt requests, try disabling the unused port using System Setup.
After that...
System - Devices - Conflicting device - Resources
Turn off the Auto Setup feature. In the "List of Resources" window, select the resource type, click the "Change" button and in the "Value" field, specify a new (unused) interrupt request value or I/O address.
Setting Parallel Port Parameters
Parallel ports are abbreviated LPT. The computer automatically assigns addresses LPT1 to LPT3 to each detected parallel port.
If you install a second parallel port, make sure it does not use an existing interrupt request. On some computers, LPT1 and LPT2 use IRQ7 by default. Using Device Manager, set IRQ5 for LPT2. If this is not possible, use your system's CMOS Setup program.
Standard Parallel Port Resource Settings
| LPT port | Interrupt Request | I/O address |
| LPT1 | IRQ7 | ZVS |
| LPT2 | IRQ7 | 378 |
| LPT3 | IRQ5 | 278 |
Setting Serial Port Parameters
Each serial port is identified by one of eight possible COM addresses - COM1, COM2, etc., each of which has its own unique I/O address and interrupt request.
Be careful when installing a device that requires a COM port into your PC. The COM1 and COM2 ports have standard I/O addresses and interrupt requests that should not be changed anywhere (usually can only be changed in the Setup CMOS program of your PC). If you need to assign a COM1 or COM2 port to a new device, then when you boot the PC, enter the Setup program and either disable the serial port assigned to COM1 or COM2, or, if you need to clear the corresponding settings for the added device, change the interrupt request and address identifying it I/O
Note that all standard I/O addresses only use the third and fourth interrupts. Since two devices should not share the same interrupt request, try to map new external devices to port COM3 over COM3 by manually setting interrupt requests and I/O addresses using Device Manager (dialog box "Properties: System").
Standard Serial Port Resource Settings
| COM port | Interrupt Request | I/O address |
| COM1 | IRQ4 | 3F8 |
| COM2 | IRQ3 | 2F8 |
| COM3 | IRQ4 | ZE8 |
| COM4 | IRQ3* | 2E8 |
| COM5 | IRQ4* | ZEO |
| COM6 | IRQ3* | 2EO |
| COM7 | IRQ4* | 338 |
| COM8 | IRQ3* | 238 |
*Can be installed using Windows 9x Device Manager (Properties: System)
Serial Port Optimization
The computer has one or two built-in 9-pin serial ports, usually located on the back of the computer. Using such a port, only 1 bit of data can be transferred per unit of time, while through a parallel port - 8 bits. The speed of the serial port depends on the universal asynchronous transceiver (UART), which converts the parallel data stream passing through the PC bus into a single-bit one.
Typically, modern PCs come with a 16550 UART model. In this case, the maximum throughput is 115 kbps, which provides sufficient bandwidth for most serial devices. Older UART models 16450 and 8250 can no longer cope with this task. But sometimes the performance of the UART 16550 may not be enough, because some analog modems process compressed data at a speed of 230 kbps, and ISDN adapters - up to 1 Mbps. So, if you need higher data transfer speeds, buy an expansion card with a 16750 UART model capable of running at 921 kbps.
Working with Parallel Ports
Parallel ports are typically used for printers, although they can also connect other devices, such as scanners, to a PC. With their help, you can transfer data at speeds from 40 KB/s to 1 MB/s, and sometimes even higher.
Basically, all PCs come with one parallel port in the form of a 25-pin connector on the back panel. To add a second port, you need to buy an I/O controller and install it in the expansion slot on the system board. There are four types of parallel port - unidirectional, bidirectional, enhanced capabilities (EPP port) and enhanced capabilities (ECP port). Each of them has different speeds and capabilities. Most new PC ports support all four modes, and to find out which one provides a parallel port, look in your PC's CMOS Setup utility under the Integrated peripherals section.
Unidirectional port sometimes also called SPP port. This basic configuration passes data at a speed of 40-50 KB/s in only one direction - to the printer or other external device.
Bidirectional port. Provides two-way data exchange with transfer speeds from 100 to 300 KB/s between a PC and an external device. In this case, information about the state of the latter enters the computer.
Enhanced Port (EPP). Designed for external drives and network adapters that require high performance. Provides data transfer speeds from 400 KB/s to 1 MB/s or more.
When installing the EPP option in the System Setup program, versions 1.7 and 1.9 are offered. For almost all peripherals purchased in recent years, you need to choose 1.9.
Extended Capability Port (ECP). Increases the speed and expands the capabilities of data exchange between an external device and a computer. If the printer and other peripheral devices support ECP, they directly report device status and errors.
If in the program. System Setup set the ECP option, then a line will appear to select a DMA channel (direct memory access channel). It must be set in the same way as for an interrupt request. To prevent DMA channel conflicts, view the free ones in the window "Properties: Computer", as described above. If the conflict cannot be avoided, then return to bidirectional port mode.
The best port for a data hurricane.
In new systems and peripheral devices, parallel and serial ports began to be replaced by a universal serial bus ( Universal Serial Bus, USB). With its help, you can achieve data transfer rates of up to 12 Mbit/s, and also connect, with just one port, keyboards, monitors, mice and many other (up to 127) devices, which, as with the SCSI interface that solves similar problems, can be connected "chain". In this case, only one interrupt request is used. The USB bus can also be installed on older computers by purchasing the appropriate expansion card.
Serial ports
Serial ports for exchanging data with external devices are the most important component of any MK; without them, its “communication” with the outside world is sharply limited. They are called sequential because only one bit is transmitted at a time (in some cases, simultaneous transmission and reception is possible, but still only one bit at a time). The most important advantage of serial ports over parallel ones (when whole bytes or nibble-tetrads are exchanged simultaneously) is the reduction in the number of connections. But it is not the only one - paradoxically, serial interfaces give a significant head start to parallel ones at high speeds, when transmission reliability begins to be affected by delays in the lines. The latter cannot be made strictly the same, and this is one of the reasons that serial interfaces are now beginning to dominate (typical examples: USB and Fire Wire instead of LPT and SCSI, or Serial ATA instead of IDE).
In microcontroller devices with our volumes of data, of course, the transfer speed concerns us secondarily, but the number of connecting wires is a very critical factor. Therefore, all external devices that we will consider further will have serial interfaces (except for displays for displaying information, for which, alas, serial interfaces are found only in fairly high-level models).
Almost any serial port can be simulated in software using regular MK pins. Once upon a time, this was done even in the case of the most popular of these ports - UART. However, since then, MKs have acquired hardware serial ports, which, however, does not mean the need for their absolute use. The ease of software simulation of serial ports is another advantage.
Of all the types of ports that may be present in an AVR MCU, we will especially pay attention to UART ( Universal Asynchronous Receiver‑Transmitter, universal asynchronous transceiver). UART is the main part of any device that supports the RS-232 protocol, but not only it (it’s not for nothing that it is “universal”) - for example, industrial standards RS-485 and RS-422 are also implemented via UART, since they differ from RS -232 only by electrical parameters and permissible speeds, and not by the general logic of construction.
Personal computers have a COM port that operates using the same RS-232 protocol, and the UART node is also its basic part. Therefore, UART serves as the main way to exchange data between the MK and a computer.
Note that the lack of a COM port in most modern PC models is not an obstacle - there are USB-COM adapters, and an additional card with COM ports can be inserted into the desktop model. How to handle UART in practice is described in chapters 21 And 22 , in relation to the platform Arduino– programming such an exchange in assembler is much more difficult (although more reliable, see below). IN chapter 22 we will see that there are simple and at the same time quite reliable ways to organize transmission through a serial port over a radio channel, which allows you to do without wires at all.
In addition to UART, almost all AVR MCUs contain the simplest of all serial ports - SPI ( Serial Peripheral Interface, serial peripheral interface). The SPI device was mentioned in Chapter 16. Its fundamental simplicity played a partly bad role - it is difficult to find two devices where the SPI protocols are completely the same, usually exchange via this port is accompanied by one or another “bells and whistles”. It should be noted that AVR programming is also carried out via SPI, however, in general, this interface and SPI for data exchange are different things, although in most cases they have the same pins.
By the way, familiar memory cards (“flash drives”) are also addressed via a protocol very close to SPI.
In addition to these ports, a very simple hardware, but more complex from a software point of view and rather slow 12C interface is often used (in Atmel AVR terminology it is called TWI ( Two‑Wire Interface, two-wire interface). With its help you can communicate with many devices: real-time clocks, compasses, sensors, and some types of memory. We will look at it again in the chapters devoted to Arduino .
The AVR has a 10-bit SAR ADC (see chapter 17). Working with it has quite a lot of nuances, and we will consider it in detail in chapter 20. IN chapter 22 you will see how much Arduino simplifies this process. And in general, we will look at some other components of the AVR family of microcontrollers as we present specific diagrams - it will be clearer this way. Now we will finish our protracted acquaintance with the microcontroller and turn to the question of how to program it. We will devote the next two chapters to basic information about programming MKs in assembly language, and then we will move on to high-level (and even ultra-high) languages. This way you can visually compare and even, if you wish, “feel with your hands” the advantages and disadvantages of one or another approach and the limits of their applicability.
Serial and parallel I/O ports
External motherboard connectors: PS/2 (1 - mouse, 2 - keyboard), network RJ-45 (3), USB (4),
D-subminiature (9-pin COM port (5), LPT port (6), VGA port (7), MIDI) (8) and
3.5mm audio I/O (9)
A (personal) computer port is designed to exchange information between devices connected to the bus inside the computer and an external device. So, the AGP bus connector is actually a port.
To communicate with peripheral devices, one or more I/O controller chips are connected to the computer bus.
The first IBM PCs provided
· built-in port for connecting a keyboard;
· up to 4 (COM1 ... COM4) serial ports (eng. COMmunication), usually used to connect relatively high-speed communication devices using the RS-232 interface, such as modems. The following motherboard resources were allocated for them:
basic I/O ports: 3F0..3FF (COM1), 2F0..2FF (COM2), 3E0..3EF (COM3) and 2E0..2EF (COM4)
IRQ number: 3 (COM2/4), 4 (COM1/3);
· up to 3 (LPT1 .. LPT3) parallel ports (eng. Line Print Terminal), usually used to connect printers using the IEEE 1284 interface. The following motherboard resources were allocated for them:
Basic I/O ports: 370..37F (LPT1 or LPT2 only on IBM computers with MRA), 270..27F (LTP2 or LPT3 only on IBM computers with MCA] and 3B0..3BF (LPT1 only on IBM computers with MCA )
IRQ number: 7 (LPT1), 5 (LPT2)
Initially, COM and LPT ports were not physically present on the motherboard and were implemented by an additional expansion card inserted into one of the ISA expansion slots on the motherboard.
Serial ports were typically used to connect devices that needed to quickly transfer a small amount of data, such as a computer mouse and an external modem, and parallel ports were used for a printer or scanner, for which large-volume transfers were not time-critical. Subsequently, support for serial and parallel ports was integrated into chipsets that implement the logic of the motherboard.
The disadvantage of the RS-232 and IEEE 1284 interfaces is the relatively low data transfer rate, which does not satisfy the growing needs for data transfer between devices. As a result, new standards for USB and FireWire interface buses appeared, which were designed to replace the old I/O ports.
A special feature of USB is that when many USB devices are connected to a single USB port, they use the so-called. hubs (USB hubs), which in turn communicate with each other, thereby increasing the number of USB devices that can be connected. This USB bus topology is called “star” and also includes a root hub, which, as a rule, is located in the “south bridge” of the computer motherboard, to which all child hubs (in this particular case, the USB devices themselves) are connected.
The IEEE 1394 bus provides data transfer between devices at speeds of 100, 200, 400, 800 and 1600 Mbit/s and is designed to provide comfortable operation with hard drives, digital video and audio devices and other high-speed external components.
FireWire, like USB, is a serial bus. The choice of a serial interface is due to the fact that to increase the speed of the interface it is necessary to increase the frequency of its operation, and in a parallel interface this causes increased interference between the parallel cores of the interface cable and requires a reduction in its length. In addition, the cable and parallel bus connectors are large.
Simple and easy
The connection point for all USB devices is the computer. Only with him can they “communicate” directly. This connection is called “point-to-point”.
When you connect it for the first time, the USB device is automatically detected by the operating system, after which it searches for the required driver. In this case, the rule applies: the newer the version of the operating system used, the higher the likelihood that the user will not have to install the driver himself. For example, Windows XP and Vista automatically recognize flash drives, card readers, and external hard drives and register them as removable drives. The drivers required for these devices are included in the Windows distribution and are always at hand on the system. Windows Vista also has additional drivers for the most common models of printers, scanners, gaming keyboards and other devices.
With rare exceptions, USB gadgets can exchange data with each other only through the mediation of a computer. In this case, the PC plays the role of a so-called USB host. It asks each device connected via USB and called a client for information about the availability of data necessary for transfer, after which it organizes a “dialogue”. It is prohibited to transfer files “on your own initiative” to clients. This method, called polling, although it takes up some system resources, makes it possible to create simple and, as a result, inexpensive USB devices.
Direct communication between two USB gadgets is possible using On-The-Go technology. Its use will allow you to print images without the mediation of a computer or directly exchange music files between MP3 players.
Competitive advantages
USB Standards
USB 1.1. Computers manufactured before 2002 provide the user with a USB 1.1 interface. Data transfer using this standard is quite slow. Theoretical peak throughput is 12 Mbps (or 1.5 Mbps). For input devices - keyboard and mouse - this is quite enough.
On a note. The earlier version, USB 1.0, did not gain distribution and remained on paper. Finished products that meet this standard have not been marketed.
USB 2.0. Computers and laptops manufactured after 2003 typically have USB 2.0 ports. The maximum speed has increased noticeably compared to the 1.1 standard and amounted to 480 Mbps (or 60 Mbps). Although in practice it is not possible to achieve this level of throughput.
Higher throughput is provided by USB 2.0 devices marked with the “USB 2.0 Hi-Speed” logo. If “USB 2.0 Full-Speed” is indicated on the box or case of the device, this means that data will be transferred at the speed of the USB 1.1 standard.
Fortunately, all USB versions are fully compatible with each other. Regardless of whether you own an old or a completely new computer, if it is equipped with USB ports, then you can connect any device with such an interface to it. So, for example, a mouse that supports the USB 1.1 standard can also be connected to a USB 2.0 connector. Conversely, USB 2.0 devices will be “understood” by slow USB 1.1 specification ports (in Full-Speed mode; for example, a USB 2.0 hard drive connected to a USB 1.1 connector will transfer data at only 1/40th the speed maximum available to him).
USB 3.0. The next version of the USB standard is already in the final stages of development. The first computers and peripheral devices equipped with a USB 3.0 interface are expected to appear on the market next year.
Keyboards
The name of such a familiar and at first glance simple PC component as a keyboard - keyboard - can literally be translated from English as “key board”. And this is no coincidence: it is impossible to imagine working on a computer without this device.
The keyboard is the main intermediary between a person and electronic equipment of many types: from personal computers to mobile phones. Despite the venerable age of the keyboard (it was used on typewriters even before the advent of computers) and the development of alternative, “humane” interfaces - pointing devices and speech recognition technologies, without a keyboard it is impossible to work on a computer, or in some cases even play games. There is no reasonable alternative to keyboards yet, there are only their various modifications and varieties that perform the same basic functions and a number of additional ones, depending on the user’s requests.
Keyboard design
Device
Attention
Some mid- and high-price USB keyboards can be used as USB splitters (hubs), as they are equipped with USB ports for connecting card readers, flash drives and other drives, as well as peripheral devices with a similar interface. Such solutions are quite convenient, especially for owners of desktops with a minimum number of USB ports (which are also difficult to access), but they are significantly more expensive than standard models.
How the keyboard works
The process of processing keyboard input is provided by two microcontrollers: one is located on the computer motherboard, the second is built into the keyboard itself. Thus, the PC keyboard itself is a separate computer system.
As can be seen in the diagram, all horizontal lines of the key matrix are connected through resistors to the power source. The built-in keyboard chip has two ports - output and input. The first is connected to the vertical (Y0–Y5) lines of the matrix, and the second is connected to the horizontal (X0–X4).
The keyboard controller works according to the following algorithm. By setting the voltage level corresponding to logical zero on each of the vertical lines in turn, the keyboard microcomputer continuously evaluates the state of the horizontal lines - regardless of activity on the central processor.
If no key is pressed, the voltage level on all horizontal lines corresponds to a logical one. As soon as the key is pressed, the vertical and horizontal lines corresponding to the key will close. When the processor sets the vertical line to a logical zero value, the voltage level on the horizontal line will also correspond to a logical zero.
If a logical zero level appears on one of the horizontal lines, the keyboard processor will record a key press. It will send to the computer (via an internal 16-byte buffer) an interrupt request and the key number in the matrix (called a scan code - this is a random value chosen by IBM back when it created the first keyboard for the PC). Data exchange with the computer will be repeated when the previously pressed key is released.
The scan code is uniquely associated with the keyboard wiring and does not directly depend on the markings printed on the surface of the key. But the program does not need the serial number of the pressed key, but the ASCII code corresponding to the character on this key. It is important to understand that this code does not completely depend on the scan code, because several values can be assigned to the same key. This also depends on the state of other keys (for example, the 0 button is also used to enter a character when it is pressed together with the button) and system settings. This is what allows you to vary the keyboard layout (that is, the order of the keys on it).
All scan code to ASCII code conversions are performed using software. As a rule, these functions are performed by the corresponding BIOS modules. To encode Cyrillic characters, these modules are extended by keyboard drivers (they are now included in operating systems).
Away from the standards
If you are not interested in reading about standard keyboards, take a look, for example, at http://onegadget.ru and read the publications tagged “Keyboard”. It talks about a special desktop keyboard for typing SMS messages, and about a variety of gaming, design, ergonomic and mobile models... Not very useful, perhaps (after all, it is extremely difficult to purchase these devices in our country), but incredibly interesting! We will not delve into the exotic, but will name only some of the most common types of non-standard keyboards.
Portable. They are smaller than standard ones and usually have 83 keys that are set almost flush together (with a center distance of 13–15 mm instead of the usual 19). First of all, portable keyboards are typical for laptops.
The category of portable includes not only reduced, but also composite models, in which the numeric and typing blocks are autonomous (there are also models in which the typing block consists of two parts), as well as collapsible keyboards, from which the numeric block is removed (in order to save space or for other reasons) can be disconnected. The feasibility of such a decision can be debated, as well as the merits of keyboards in the next category.
Ergonomic. Concerned about the health of users who spend a lot of time at the computer, manufacturers are increasingly producing keyboard models whose body shape and relative position of the keys correspond to the natural position of a person’s hands. Almost all ergonomic keyboards have a built-in palm rest (usually non-removable, but options are possible). The rows of alphabetic keys on them are divided and rotated relative to each other, as a result of which their arrangement becomes V-shaped, and the entire keyboard is S-shaped. However, a user accustomed to a standard-shaped keyboard (especially if he types “touch”) will find it difficult to adapt to an ergonomic model.
Multimedia. Recently, almost all manufacturers are equipping keyboards with additional buttons, with which you can, for example, control music or video playback. There are even specialized models “tailored” for multimedia centers. Thanks to the drivers that come with this keyboard, the functions of the additional keys are usually easy to change.
Mobile. They are designed for use in conjunction with a pocket computer, communicator or ultraportable laptop (that is, with those devices whose own keyboard is not optimal for typing) and for ease of carrying they are folded or even rolled into a tube. Such models will be appreciated primarily by those who work a lot and often on the road - they are light, waterproof, and quite durable. But they are not cheap.
Gaming. For enthusiast gamers, they produce special models with short key travel and a rich set of additional buttons. In addition, certain keys, for example Ü, can be blocked on such keyboards: after all, if a gamer accidentally presses it in the heat of battle, the game will be interrupted...
Some manufacturers equip keyboards with various additional “features”, such as backlit keys for working or playing in the dark or a compact display for displaying additional information. Initially created for gamers, these options have found application in other areas: for example, displays on keyboards have already learned to use system monitoring utilities for their purposes.
Designer. For users who are particularly demanding in terms of the appearance of their equipment, there are exclusively designed keyboard models. In an era of craze for modding and tuning of everything, the whole variety of “modified” keyboards is amazing. Metal, silicone, glass, porcelain, fur, leather, rhinestones, birch bark and wood, painting... Many companies specialize in creating unusual keyboards, applying airbrushing to these computer accessories and even painting them “Khokhloma.” Of course, there is no practical benefit in decorating keyboards. And you need to treat such delights critically and carefully - due to the same concern for your own health. And the rest is a matter of taste and wealth...
This category also includes keyboards, the buttons on which are equipped with small displays with images that change depending on the running program. The most popular representative of this class of devices is the Optimus Maximus keyboard, developed by Artemy Lebedev’s studio. This model is incredibly expensive: about 44 thousand rubles, that is, 50 times more expensive than a high-quality middle-class keyboard. You can try to understand why they are asking for such crazy money by reading the blog materials of the Optimus project (within the framework of which several more models of “keyboards of tomorrow” are being produced) – http://community.livejournal.com/optimus_project.
Laser. The only tangible component of such a keyboard is the compact “box” of the projector. The beam of light it emits “draws” the keys on the table surface, and infrared sensors monitor when and which of them the user “presses.” Such devices are expensive, and their ease of use still leaves much to be desired: they do not support high-speed printing.
Attention
To expand the capabilities of a portable laptop keyboard, use an additional modifier key. Combined with alphabet, number and function keys, it even allows you to control your PC hardware settings. For example, pressing + e on some computers decreases the screen brightness, and + f increases it. Features of using the modifier depend on the laptop model.
Buying Tips
Be sure to test several models presented in the store. The characteristics of the keyboard that are significant to the user can be assessed literally at the fingertips. Unlike most computer components, which can be selected “in absentia” based on the contents of the list of technical characteristics, the keyboard can only be evaluated through direct contact.
Perform a series of keystrokes, or better yet, type a few sentences of real text. Pay attention to the tactile characteristics of the buttons. Are the size of alphanumeric keys and the spacing between them comfortable for you? Do the shape and size of the í, r, and w keys, which even on standard keyboards often increase and decrease, suit you? Are you satisfied with the key travel (is it too large or too small)? Are they resilient enough? Do the keys have a clear press response (tactile and auditory)? Is there a lot of play in the buttons in the horizontal plane? All these little things are far from unimportant, as it might seem at first glance: people actively working with texts make tens of thousands of keystrokes during the day! Touch typists also definitely need to pay attention to the presence and convenience of protrusions on the A and O keys, as well as on the 5 button in the number pad.
Push-button keyboards can be either with or without a “click”. “Click” is a click characteristic primarily of mechanical devices, but it is also found in relatively expensive models of other types. The “click” is implemented using an arc-shaped thin plate under the key (which bends with a jerk, making a sound) and allows you to determine by ear that the key is pressed and not miss letters when typing quickly. If you work at a computer in a separate room and the clicking of the keys does not bother anyone, choosing a “clicky” or “quiet” keyboard is purely a matter of personal preference. If you have to hit keys at home (especially at night), in a cramped office space or in a public place, it makes sense to purchase a keyboard without a “click”.
In addition to the design, the appearance of the device is important when choosing. For a long time, desktop keyboard cases and buttons were made of standard light gray plastic. Sometimes some of the keys (mainly service and functional) were painted a darker color; There is no noticeable benefit in such a solution; it is rather a design one. Then keyboards in black and white began to appear, and for some time now models painted in a variety of colors have been produced and sold. The ability to choose a keyboard that matches your desk or other room décor is nice, but it shouldn't be a problem. Imagine spending long hours in front of a hot pink keyboard, and you probably won't want to place this device in front of you, which is guaranteed to serve as an additional source of stress and eye strain.
Characters on dark-colored keys are often difficult to read, so we recommend purchasing white keyboards (such as those found on Apple computers) or models with light gray keys (often referred to as “computer gray”). It is desirable that the Latin and Cyrillic characters be applied to the buttons not only in a high-quality and distinguishable manner, but also in different colors. This will allow you to avoid getting confused with the keys, trying to determine whether you are pressing “eh” or “en”, “er” or “pi”...
All of the above is true for both desktop computers and laptops. But the evaluation of a laptop keyboard should be approached even more carefully, since it can only be replaced with another one together with a mobile computer.
A more expensive keyboard is not always better. Price, of course, is a significant factor, but individual comfort, in general, does not depend on it: the cheapest model from an unknown manufacturer may be the most convenient for you. Wired or wireless, standard or unusual, the keyboard - like shoes or, for example, gloves - should suit you, and you, especially if you spend a lot of time at the computer.
"Safety precautions" when working with the keyboard
In light of the above (that is, given the fact that a significant part of your life is spent on a computer), it is necessary to think not only about the design and functioning of the equipment, but also about its operation. It should be remembered that not only you can harm the keyboard, but it may also be unsafe for you!
The greatest danger associated with the keyboard is contamination. Studies have shown that in some cases there are more microorganisms on the keyboard than on the walls of the toilet! Therefore, the keyboard should be regularly cleaned with wet wipes for computer equipment and shake out debris from the spaces between the keys. Before doing this, you must disconnect the keyboard from the PC or turn off the laptop. Otherwise, the device may become damaged due to random simultaneous pressing of keys during cleaning: a number of keys will stop working.
Make it a rule to never eat at your keyboard. You should also not drink near the computer: sooner or later the contents of the cup or glass will end up spilled onto the “tool of production.” Coffee and other liquids caught between the keys, after the water evaporates, leave a sticky substance inside and on the surface of the device, which is difficult to remove and interferes with operation quite strongly, because the keys start to stick.
Overworking your hands is no less dangerous than dirty keys. When working with the keyboard, the hands are in a curved position, which negatively affects the condition of the wrists, and they also hang over the keyboard for a long time, which leads to overload of the elbows and forearms.
It is not difficult to relieve your hands from excess load: you need to create support for your hands so that they do not need to hang in the air throughout the entire time you work at the computer. Paradoxically, but true: a laptop keyboard in this regard turns out to be more ergonomic than a standard desktop keyboard - most laptops, with the exception of some ultraportable models, have a support pad in front of the rows of keys. The appropriate palm rest on desktop keyboards can be created by an optional palm rest, which is included with some models, a corresponding ledge on the tabletop, or a special optional bolster. The latter solution is optimal, but such rollers, which are usually made of soft foam polymer, are rarely found on sale.
Even when working with an ergonomic keyboard, make it a habit to take breaks after every hour of work, stretching your hands and resting them. Remember how in first grade you did the simplest exercises: “We wrote, we wrote, our fingers were tired”? They remain relevant even when actively working on the keyboard in later life.
How do you type?
The choice should be based on your typing abilities and how often you use the keyboard. If you spend a lot of time at the computer, communicate a lot, or just work and type, then you need an expensive keyboard. It will be easier for you to work on it and the efficiency (efficiency) of your work will increase significantly with good peripherals. This is unequivocal and not subject to reservation. But in the case when you print little, a cheap option will be enough based on just a few tips given below.
Keyboard for music lovers.
Now it's time to take a deeper look at keyboard options. If you like to listen to music or surf the Internet often, buy a keyboard with additional features. Now there are many options that, by the way, do not spoil the quality of the keyboard itself, like a classic one, but have a number of functions for adjusting the sound, switching songs, opening a browser, checking mail, etc. All these functions will simplify your life as a gamer or music lover and are worth such a keyboard will not be too expensive.
Key hardness.
When deciding on a keyboard with additional functions or lack thereof, we think about convenience, since you still have to type texts all the time. Try pressing the keys in the store to see if they click easily. Are there any sounds made, because it happens that pressing is silent, which is completely inconvenient. The keys should be slightly hard to press and feel like they are being pressed. But we don’t buy a keyboard with tight keys, that’s also bad.
Key height.
The keys should be of medium height, too large or small - they are inconvenient, although you can get used to everything, but why?
Palm rest.
Old and new professional keyboards had a small slide in front of them, a stand for hand comfort. If you spend long hours typing texts, this is a very convenient thing, try it, maybe it’s just your choice.
Letter color.
The design itself and the color of the keyboard may be different. This is a matter of taste and harmony with other parts of the computer. If your computer is all black, then a white keyboard will not fit nicely under it. Although there is no difference, the eyes do not get used to it. The main thing is to look at the color of the letters. After all, we have English and Russian signs, which should always be different in color and be noticeable. This is especially important for people who look at the keyboard while typing. If the letters of both languages are the same color, you will get a lot of pain, your eyes will get tired and you will constantly get confused. After all, the letters “M” and “M” of the English and Russian layouts will be exactly the same.
Be afraid of the Off key.
There are often keyboards where the keys to turn off the computer, restart, and enable sleep mode are located immediately above the cursor control keys. These are the most terrible options, it is impossible to get used to them. If you don't want to accidentally turn off your computer, discard this option immediately.
Compound.
Radio.
Gadgets.
Trendy keyboards also have LED backlighting, additional screens, scrolling, a built-in mouse and much more. We won’t write about this, these are all bells and whistles that won’t make life any easier. If you want quality, it’s better to buy a regular good keyboard, the same mouse and additional input devices, but sculpting mouse functions into a keyboard is too much.
When did you buy it?
Now your choice is made and you are working at your new keyboard. Great, just don’t forget to follow up on your purchase. If after six months you managed to spill coffee on it, get it dirty with dirty hands, etc., there’s no need to think about something new again. After all, your keyboard works hard, only 1-2 keys stick a little? It's not a problem! Any keyboard is easy to clean. We turn it off, remove all the keys with a screwdriver and wash it. Just don’t forget to take a photo of everything first so you don’t get confused when reinstalling the letters. After cleaning, your keyboard will be new!
Compound.
The keyboard connects to the computer in two of the most popular ways: via the ps/2 connector or USB. Once upon a time there was an AT connector, but it is long gone. And when choosing, look at what your computer supports. New models may not have, for example, a ps/2 input, or you may only have one USB connector (useful for a flash drive). It’s better to prepare for such troubles, although in truth these are all trifles. The number of USB inputs can be easily increased with a splitter, and if ps/2 is not available, you can connect via an adapter (there are any adapters now). And when choosing a keyboard, the only thing you need to understand is about your sockets on the back of the system unit, and if your choice falls on a keyboard with a ps/2 type connection, and you don’t have one, then we immediately buy an adapter that costs a penny, without bothering at all about the lack of necessary ones nest
Radio.
You can buy a radio-controlled keyboard without a connecting cord. This is a good solution for an additional keyboard in a laptop or for people who do not like to sit in one position in a chair, but recline or even lie in front of the monitor. This is already individual, such keyboards are no different from their wired counterparts, except for the ease of portability and high cost.
Gadgets.
Trendy keyboards also have LED backlighting, additional screens, scrolling, a built-in mouse and much more. We won’t write about this, these are all bells and whistles that won’t make life any easier. If you want quality, better buy a regular good keyboard, the same mouse and additional input devices, but sculpting mouse functions into a keyboard is too much.
Care.
Now your choice is made and you are working on your new keyboard. Great, just don’t forget to follow up on your purchase. If after six months you managed to spill coffee on it, get it dirty with dirty hands, etc., there’s no need to think about something new again. After all, your keyboard works hard, only 1-2 keys stick a little? It's not a problem! Any keyboard is easy to clean. We turn it off, remove all the keys with a screwdriver and wash it. Just don’t forget to take a picture of everything first so you don’t get confused when reinstalling the keys with letters and symbols. After cleaning, your keyboard will be new!
Computer mice
A “mouse-type manipulator” (or its analogue) is an attribute of any modern computer, without which it is difficult to effectively interact with a PC both in work and in games. How does this indispensable device work?
The main idea underlying the concept of a modern PC user interface is to compare manipulations with virtual objects to operations with objects of the material world - transferring them, unfolding them, pressing virtual buttons, etc. A person performs most of them with his hands, and as a result, the most convenient manipulator is a device that directly “translates” hand movements into actions on the screen.
Using this or that technology, the mouse registers its movement in space, and its driver and operating system move the cursor around the screen accordingly. In turn, application programs running on a PC receive information from the OS that the cursor is over one or another element of their user interface, and react in a given way to mouse actions - pressing keys and rotating the scroll wheel.
Types of computer mice
Mouse pad
Rugs, so popular in the era of ball mice (when they were absolutely necessary), today have minimal practical value. The emphasis in their production has shifted to design and exclusive features: mats are produced with soft pads for the wrist, with LED backlighting or from “space” materials, which, according to manufacturers, dramatically increase the accuracy of cursor positioning...
Connection interface
The mouse can use four different interfaces to connect to a PC.
Few mice currently connect to the green PS/2 connector (the purple one is used to connect the keyboard). The disadvantage of this interface is known: you cannot disconnect or connect the mouse while the computer is running, as this can lead to a system failure. In addition, digital technology strives to unify interfaces, so PS/2 connectors are already disappearing from motherboard panels, just as the COM port, to which “ancient” mice were once connected, disappeared.
The majority of mice today have a USB interface. They can be connected and disconnected while the computer is running, and if there is no free USB port on the computer, they can be connected to the PS/2 connector using an adapter.
Mice with a radio interface do not require wires, and their signal receiver is connected to the USB connector of the computer.
Mice with Bluetooth support are more expensive than their counterparts with a conventional radio interface, but the use of a digital communication channel allows not only to protect transmitted data from interception (which is important for a few private users), but also to avoid problems associated with the mutual influence of two or more manipulators, working in the same room. Most of these models are equipped with a miniature USB adapter, that is, they can be connected to a PC that does not have a built-in Bluetooth module (most of them directly with built-in modules do not work). The disadvantage of wireless mice - both with and without Bluetooth interface - is the need to use batteries or rechargeable batteries to power them. For the same reason, wireless mice are always heavier than their “tailed sisters” and their weight is often poorly balanced.
Mouse competitors
The most promising competitors of the mouse are touch screens. The logic behind the appearance of such control devices is clear: the mouse acts only as an intermediary between
