What types of keyboard interfaces are there?

There are three types of keyboard interfaces: 1. "PS/2" interface, which is a special interface for mouse and keyboard. It is a six-pin circular interface. The keyboard only uses 4 pins to transmit data and power supply; 2. USB interface, which has become the most important interface method for various devices; 3. MIDI interface, which is a kind of hardware that connects computers and MIDI devices.

The operating environment of this tutorial: Windows 10 system, DELL G3 computer.

What are the types of keyboard interfaces?

The keyboard interface type refers to the interface method or type between the keyboard and the computer host.

Different keyboards have different interfaces. If you understand the interfaces of the keyboard, you will not find that the keyboard you bought cannot be used. Among them, the PS/2 interface can be said to be the mouse interface equipped on every motherboard. It is the most versatile. Sometimes we also call it "round mouth"; the counterpart of "round mouth" is "big mouth", which has many Found on some old-fashioned motherboards, that is, the AT interface method (rarely seen anymore). The USB interface is a product that appeared later than the first two, and the USB interface of the motherboard can not only be used to connect the mouse, but also other USB devices, and the transmission speed is higher, which also saves the PS/2 port of the motherboard. . Motherboards generally have two interfaces, PS/2 and USB.

PS/2 interface

first appeared on IBM's PS/2 machine, hence the name. This is a dedicated interface for mouse and keyboard. It is a 6-pin circular interface, but the keyboard only uses 4 of the pins to transmit data and power, and the remaining 2 are empty pins. The transmission rate of the PS/2 interface is slightly faster than that of the COM interface, and it is the standard interface of the ATX motherboard. It is one of the most widely used keyboard interfaces.

Both the keyboard and mouse can use the PS/2 interface, but according to the PC'99 color specification, the mouse usually occupies the light green interface and the keyboard occupies the purple interface. Although the working principles of the two interfaces are the same from the above pin definitions, the two interfaces cannot be mixed. This is determined by their different signal definitions inside the computer.

USB interface

The full name of USB is Universal Serial Bus. USB supports hot-swap and plug-and-play advantages, so the USB interface has become the preferred choice for many devices. The most important interface method. USB has three specifications, namely USB1.1 and USB2.0 and the emerging USB3.0.

There is not much difference in use between keyboards with PS/2 interface and USB interface. Since the USB interface supports hot swapping, USB interface keyboard may be slightly more convenient to use. However, the underlying computer hardware supports the PS/2 interface more fully, so if the computer encounters certain failures, the keyboard using the PS/2 interface will have better compatibility. Mainstream keyboards use either PS/2 interface or USB interface. You need to choose according to your needs when purchasing. Various keyboard interfaces can also be converted through specific adapters or cables, such as USB to PS/2 adapters.

MIDI interface; MIDI interface is a kind of hardware that connects computers and MIDI devices. It is also a standard for digital music.

The keyboard interface type refers to the interface method or type between the keyboard and the computer host. There are two common keyboard interfaces on the market: PS/2 interface and USB interface. There is also an old-fashioned AT interface that is no longer common, commonly known as "big mouth". It has been basically eliminated, so it will not be introduced.

The difference between keyboard interface ps2 and usb types

To put it simply: a data packet of the USB keyboard has only 8 bytes (why only 8, this is because the protocol stipulates, why the protocol stipulates this, because in the early days, the USB speed was slow, and the maximum number of packets transmitted using interrupts was 8 bytes), of which 2 bytes mark the status, and the remaining 6 bytes are used To record the scan code of the currently pressed or popped-up key, therefore, the USB keyboard can describe the status of up to 6 keys at the same time.

This deceptive design specification of the USB keyboard results in that it can only achieve up to 6 keys without rollover. To solve this problem, the USB keyboard specifications must be redesigned, but I guess no one is willing to do this, because this thing works well, and most people will not press 6 keys at the same time.

As for the PS/2 keyboard, this specification is not used. PS/2 is: report whatever is pressed, and report whatever is popped up. If 10 keys are pressed at the same time, 10 will be reported in sequence. There is no protocol limit on how many key press events can be recorded at the same time. It depends on the operating system itself. Therefore, the PS/2 keyboard can theoretically achieve unlimited key presses without rollover.

Of course, some people have indeed seen USB keyboards break the 6-key limit. One of the possible reasons is: the USB device built into this keyboard is a multiple keyboard USB HUB, because USB allows multi-level Device connection, so you can break the 6 limit.

Of course, it is also a solution to bring the USB keyboard with its own driver, because although the interrupt transmission only has 6 bytes, the Bulk transmission can transmit 256 bytes without any problem. (Note: I searched on Baidu myself and found that although many manufacturers have implemented USB full-key rollover, there seem to be a lot of bugs. It seems that the technology still needs to be developed.) In short, the specifications are the specifications, and there are always those that are not restricted by the specifications. Method.

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