USB Adapters & Adapter-Cables
These are adapters or short USB cables that are used to convert among different USB cable types, and make them compatible with each other or different USB ports. They have a different USB connector-type at each end, or if the same USB connector is used at each end, they are called "USB Gender Changers."
A USB adapter is a device that performs the function of a protocol converter between two devices where one device utilizes the proprietary Universal Serial Bus (USB) protocol. This facilitates efficient, effective and convenient communications between the devices.
The Universal Serial Bus protocol is a key electronics industry standard that oversees the specifications for specific classes of cables and connectors. It was developed in 1996 as a collaborative effort between Compaq, Nortel, IBM, and others. The term 'bus' incidentally relates to a system for data transfer between computers or the components within a single computer.
The USB standard covers the protocol for connection, communication, and power for computers and peripheral devices in a hierarchical manner and has had four generations so far, each with increasing rates of data transfer.
It was created to standardize and simplify the connection of peripherals to computers and is self-configuring and hot-pluggable, characteristics that make it extremely convenient for both industry and consumer use.
By connecting a USB adapter, devices become interoperable as the protocols of the alternately networked device are converted to the USB protocol for use and vice versa. The relevant protocols for both the computer and peripheral are stored on routers which can convert the transmitted data. The conversion process includes the transfer or translation of data formats and data rates to comply with USB.
USB adapters have a number of key functions that initially arose from their primary purpose of standardizing the connection of peripherals to computers. The USB connector end of an authentic USB adapter will bear the USB logo, signifying that the adapter has cleared compliance testing and that it will work as expected.
USB to serial port adapter.
This adapter converts the serial port, a serial communication interface that has sequential data transfer, one bit at a time. It is a predecessor to USB and is typically used for:
- Screens and terminals
- Other peripheral devices
The serial port typically complies with the RS-232 protocol, also known as Recommended Standard 232. This standard has existed since the 60s and oversees serial communication data transmission.
Because it is simple and cheap with little necessary supporting software, the serial port is still in use in a wide range of peripheral hardware and devices including:
- EPoS hardware and peripherals
- Automation equipment
- Testing and Measurement equipment
- Networking hardware and cabling
- Screens and Projectors
A USB to serial port converter facilities compatibility. USB adapters also exist for RS-485 and 422 which have predominantly industrial applications.
USB adapters for DC power supply
USB routinely facilitates downstream power transfer in a host and connected device relationship. The transfer of electrical current is unidirectional, unlike data transfer which is bidirectional.
There are 3 key classes of downstream USB port that accommodate charging:
- Standard Downstream Port (SDP) operates at 0.1A to 0.5A and is the type of charging port on computers and laptops.
- Downstream Port (CDP) carries DC current at up to 1.5A
- Dedicated Charging Ports (DCP) include wall sockets that carry an in-built USB power adapter and power modules which transfer current at a rate greater than 1.5A for active charging of devices
USB power delivery is supplied typically at 5 volts with a 5% variance. Pins within a USB connector transfer data (D+ and D-) and externalized pins carry current. Each pin is connected to a wire, with four wires in a USB charging cable. The higher specification USB 3.0 carries an additional 5 pins for even faster charging. Mains charging via a USB adapter requires conversion of mains voltage to the standard 5V.
Multiple devices can be charged simultaneously via the USB ports, though the charging will be at a sub-optimal rate. Higher specification 'superspeed' USB is able to adequately handle a greater amount of load and charge multiple devices quickly.