A keyboard is the part of a computer system that enables the user to control certain aspects of the computer. It allows a user to enter data, compose written verbiage and do other useful tasks. When a user depresses a key on a keyboard, a change in the current flowing through the circuit associated with that key occurs. In the keyboard, a number of key switches corresponding to the keys are arranged in matrix on the intersections of drive lines and receive lines. The keyboard includes one or more keys with symbols such as the letters A to Z and numbers and punctuation marks. A keyboard may also typically includes additional keys of various sizes such as a space bar, an enter key and the like. The keyboard is provided with a microcontroller which performs predetermined processing in response to key press and key release operations. Depending on which key circuit carries the signal to the microcontroller, the microcontroller generates a number, called a scan code. Each key has a unique scan code. The microcontroller detects the change in current from a depressed key. To distinguish between a current change that results from a depressed key and an aberrant current fluctuation that results from key bounce, the microcontroller scans the key switch matrix hundreds of times each second. Only current changes that last for two or more scans are acted upon by the microcontroller.
Keyboards typically come in two basic configurations: wired and wireless. Most keyboards are connected to the computer by a length of electrical cable, and are designed to be used in a fixed horizontal manner as with a conventional typewriter. As the PC has become more popular in general households, there has been a problem that the cable is obstructive or too short for satisfactory use. The computer user is severely restricted in terms of physical location and movement, and is typically required to be a foot or two in front of the computer monitor screen. Another disadvantage of the standard keyboard is that it consumes otherwise usable space, such as area on a desktop. The fixed type of keyboard cannot as easily be used in the standing position if it had been previously adjusted for use while sitting, and the keyboard is impractical were the user to assume a reclining position because the keyboard requires a stable horizontal platform for mechanical stability. While such keyboards are generally connected to PC main bodies via cables, various peripherals including keyboards and pointing devices such as mice are also connected to the PC main bodies, so that cables for connecting them are often complicated, causing troubles for deskwork frequently. While wired keyboards are generally less expensive, wireless keyboards are becoming more popular because they eliminate the need for cords that otherwise clutter up the workspace. Thus, both types of keyboards are found in a variety of settings, depending on what is needed.
In order to solve the problems that occur because of keyboard device and/or mouse device being wired to computer main body, many keyboards have evolved from wired and limited range operations to wireless and remote operations. Wireless keyboards have a number of advantages over the more common wire connected keyboards employed in computer systems. Wireless keyboards enable computer users to input data from positions spaced from the remainder of a processor-based system. This gives the user the additional freedom to make data entries without requiring the user to sit proximate to the processor-based system. Wireless keyboards offer more flexibility to the user to position him or her self relative to the computer. This can reduce strain and tiredness associated with computer use. Wireless keyboards reduce the amount of wires connected over or around a desktop and reduce clutter and complicated wiring tangles. As more add on peripherals are included in typical computer systems to support more advanced performance, the removal of cable wiring for a keyboard is of particular importance in saving space around the computer body. This creates a cleaner look to the overall system and can give the computer system a more sophisticated and/or expensive look. With the wireless keyboard, the installation and operation become simple because wiring cable is not needed for data transmission to computer, and numbers of users are able to use a computer simultaneously by connecting numerous keyboards to a computer. On consideration of convenience, wireless keyboard are popularly used with various computing apparatuses, e.g., desk-top computers, notebook computers, personal digital assistants, mobile phones, and pocket computers.
The wireless keyboards currently available are either infrared based or RF based transmission systems. Wireless keyboard transmits data to the central processing unit (CPU) of the computer via either radio frequency (RF) signals or infrared (IR) signals. In a wireless keyboard, a microcontroller scans the key matrix to detect which keys are pressed, and transmits key data corresponding to the pressed keys via infrared or radio waves. Each time the keyboard sends a wireless key make code to the host computer indicating that a key has been depressed, the host computer awaits a key break code indicating that the key has been released. If the key make code is not followed within a predetermined time frame by the break code, the operating system automatically repeats the key represented by the make code. The delay between the make code and automatic repeat is user configurable. The wireless keyboard contains an infrared or radio frequency transmitter, and typically a small receiving unit is located in the vicinity of the computer and connected to it by electrical cable. Current wireless keyboards employ the same transmission formats, or schemes, used with hardwired keyboards. Typically, each of the keys of a keyboard are treated as a position in a matrix. The index of the matrix position of a particular key character is transmitted to the computer via pulses of light. An infrared wireless keyboard simply uses an infrared transmitter in the keyboard and an infrared receiver in a computing apparatuses to establish a link between the keyboard and the computing apparatus. Radio frequency (RF) wireless keyboards use RF antennas for transmitting RF signals. For a wireless keyboard, battery capacity is a critical design parameter. By reducing the power consumed when transmitting key characters to the computer, the battery can be advantageously made smaller while maintaining battery life between recharging. Another advantage of reduced power consumption is longer battery life.
The use of wireless IR communications has been known for quite some time. A typical application for such IR communications has been, and is currently, for remote control of electronic devices such as television sets, video cassette recorders, home audio systems, etc. In a wireless IR keyboard, each time a keyboard key is pressed a digital code corresponding to the pressed key is generated, modulated onto an IR carrier, and transmitted to the special set top box. The set top box receives the IR signal, decodes the signal and determines which key was pressed. An infrared wireless keyboard system allows multiple users to operate wireless keyboards without interference. Infrared wireless keyboard systems can accommodate multiple users with multiple channels. Each channel is programmed with an individual identifier code and an individual carrier frequency. When a key is depressed, the key code and ID code are transmitted according to the known RS-232 format at a designated frequency. The carrier frequency is designated by the user, and is selected from a range of frequencies. The receiver, which is coupled to the computer system, can determine from the received ID code which channel the keyboard is using. The infrared wireless keyboard typically operates on a six-volt power source that is commonly derived from four 1.5-volt batteries. The infrared systems are the simplest and least expensive, however, they require a line of sight to the receiver. This can result in inconsistent transmission as the keyboard is moved or if other objects block the transmission path. RF systems do not suffer from this problem but are more expensive than infrared systems. The reliability of transmission in RF systems at a given range depends on the RF frequency and the power and quality of the transmitter.
While wireless keyboards are becoming acceptable substitutes for cable keyboards, there are still problems associated with wireless transmission. The primary reason that wireless keyboards have not displaced wire connected keyboards to a greater extent is the need for replacing batteries. When batteries fail in a wireless keyboard computer system the system is useless until the batteries are replaced. In some occasions, an input from a wireless keyboard to an information processing device is hindered by communication incapability depending on a relation between positions of the information processing device and the wireless keyboard. The wireless keyboard may have a relatively limited effective range. If the keyboard is moved too far away from the host processor-based system, the link may be lost. Similarly, if severe interference is encountered, the link may be lost as well. The infrared wireless keyboard has large power consumption requirements because of the infrared transmitter. The increased power consumption reduces overall battery life so that the batteries must be replaced more often. Radio frequency (RF) wireless keyboards addressed some of the shortcomings of the infrared wireless keyboards. However, the production costs associated with the RF wireless keyboard are high because complex antenna circuitry is used. Moreover, in some instances even the complex and expensive antenna circuitry still lacks the efficiency for transmitting RF signals....