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No device detected. Both lines are pulled down by 15 kΩ pull-down resistors on the host side. SE0 ≥ 2 μs Connect USB device pulls up either D+ or D− to wake the host from the detached line state. This starts the USB enumeration process. This sets the idle state. D− pull-up D+ pull-up As full speed, then chirp in reset: Idle / J
The throughput of each USB port is determined by the slower speed of either the USB port or the USB device connected to the port. High-speed USB 2.0 hubs contain devices called transaction translators that convert between high-speed USB 2.0 buses and full and low speed buses. There may be one translator per hub or per port.
Juice jacking is not possible if a device is charged via a trusted AC adapter or battery backup device, or if using a USB cable with only power wires. For USB cables with data wires, a USB data blocker (sometimes called a USB condom) [25] can be connected between device and charging port to disallow a data connection. [26]
Sleep-and-charge USB ports can be used to charge electronic devices even when the computer that hosts the ports is switched off. Normally, when a computer is powered off the USB ports are powered down. This feature has also been implemented on some laptop docking stations allowing device charging even when no laptop is present. [81]
Almost all ports on personal computers are hot-swappable. Plug-and-play ports are designed so that the connected devices automatically start handshaking as soon as the hot-swapping is done. USB ports and FireWire ports are plug-and-play. Auto-detect or auto-detection ports are usually plug-and-play, but they offer another type of convenience.
In addition, some types of computer systems do not treat USB devices as hot-pluggable, which means the keyboard and mouse will not be re-detected when switching back to a particular KVM port. For these types of systems, it is necessary to implement device emulation. Standard device emulation has its limitations.
Finally the call device.controlTransferOut() will set up the device to communicate through the WebUSB Serial API. Once the set up is all done, data can be transferred to the device using device.transferIn() to transfer bulk data to the device, similarly its sister function device.transferOut() to read data from the device. [17] [1]
USB On-The-Go (USB OTG or just OTG) is a specification first used in late 2001 that allows USB devices, such as tablets or smartphones, to also act as a host, allowing other USB devices, such as USB flash drives, digital cameras, mouse or keyboards, to be attached to them. Use of USB OTG allows devices to switch back and forth between the roles ...