Also, USB mice do not cause the USB controller to interrupt the system when they have no status change to report according to the USB HID specification's default profile for mouse devices. USB mice have lower latencies than PS/2 mice because standard USB mice are often polled at a default rate of 125 Hz while standard PS/2 mice send interrupts at a default rate of 100 Hz when they have data to send to the computer.
Tkeyboard class drivers#
Most modern operating systems ship with drivers for standard HID mouse designs (the most common modern mouse design has two dedicated buttons and a mouse wheel that doubles as the third button) mice with extended functionality require custom drivers from the manufacturer. USB HID mice can range from single-button simple devices to multi-button compound devices.
Not having to respond to repeated polling saves power, so the PS/2 interface is often used in laptops' internal keyboards.Ĭomputer mice are another common USB HID class device. The PS/2 interface does not interrupt the CPU at all when there are no state changes, except when a key is held long enough to activate typematic. The above-mentioned behavior is in contrast to the PS/2 (not to be confused with PlayStation 2) interface, which supports n-key rollover (NKRO) for keyboards capable of supporting it. However, keyboards in non-boot mode are free to implement an alternative HID profile. The recommended profile for keyboards that are not in boot mode in this specification limits keyboards to 6KRO and causes them to respond to an interrupt with a status report at least every half second (again, even if there is no state change) in order to implement typematic (repeating the scancode when the key is pressed long enough) unless the USB controller is programmed to tell the keyboard not to do this.
This profile is intended to allow the BIOS to handle a USB keyboard in the absence of a USB-aware operating system. These are limited to 6-key rollover (6KRO) and will interrupt the CPU every time the keyboard is polled (even if there is no state change) unless the USB controller overrides this behavior. Some keyboards implement the USB Boot Keyboard profile specified in the USB Device Class Definition for Human Interface Devices (HID) v1.11 and are explicitly configured to use the boot protocol.
Tkeyboard class Pc#
The PC 97 standard requires that a computer's BIOS must detect and work with USB HID class keyboards that are designed to be used during the boot process. The USB HID class keyboard is normally designed with an IN endpoint that communicates keystrokes to the computer and an OUT endpoint that communicates the status of the keyboard's LEDs from the computer to the keyboard. Keyboards are a common kind of USB HID class device. In this sense those devices also belong to the USB HID class.
Tkeyboard class Bluetooth#
The Bluetooth profile specification only points readers to the USB HID documentation. The same HID protocol is used unmodified in Bluetooth human interface devices.
Tkeyboard class software#
These functions allow hardware manufacturers to design a product to USB HID class specifications and expect it to work with any software that also meets these specifications.
Many predefined functions exist in the USB HID class. The USB HID class describes devices used with nearly every modern computer.
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