USB data interface type

To facilitate the download of files in the digital camera memory, digital cameras and PCs can be connected in multiple ways. The common interfaces are USB interface and ieee1394 FireWire interface.

Comparison between USB and ieee1394

The transmission rate is different.In the past, many people used ieee1394 for file transmission, because its traffic is hundreds of times faster than that of USB1.1. The USB transmission rate is currently only 12 Mbps/s, and can only be connected to low-speed devices such as the keyboard, mouse, and microphone, while ieee1394 can use 400 mbap/s, it can be used to connect devices that require high speed, such as digital cameras, scanners, and Information appliances. Later, USB was launched. Although it caught up with ieee1394, the fireline traffic could increase to 1 GB.

The two have different structures.USB must have at least one computer and hub for interconnection. Up to 127 devices can be connected in the network. Ieee1394 does not require computers to control all devices or hubs. ieee1394 can use bridges to connect multiple ieee1394 networks, that is to say, after 63 ieee1394 devices are implemented by ieee1394, other ieee1394 networks can be connected by a bridge to achieve unlimited connections.

The intelligence of the two is different.The ieee1394 network can be automatically reset when its devices are added or removed. USB is used as the hub to determine the increase or decrease of the connected device. The applications of the two are different. USB is now widely used in all aspects. Almost every PC motherboard has a USB interface, and USB will further increase the range of USB applications. Ieee1394 is currently only used in audio, video, and other multimedia. The following lists and compares several data interfaces:
 

 

USB transmission mode
Four different data transmission methods are defined in the USB specification for different system resource requirements of devices:
1.
This method is used to connect external devices that require continuous transmission and have low requirements for data correctness and are extremely time-sensitive, such as microphones, speakers, and telephones. The transmission mode transmits data continuously between the host and the USB device at a fixed transmission rate. When data transmission errors occur, USB does not handle these errors, instead, it continues to transmit new data.
2) interrupted transmission mode.
This method transfers a small amount of data, but the data needs to be processed in a timely manner to achieve real-time results. This method is mainly used on external devices such as the keyboard, mouse, and game handle.
3) control the transmission mode.
This method is used to process data transmission from USB devices on the host. Including Device Control commands, device status query and confirmation commands. After the USB device receives the data and commands, it processes the data in the queue based on the first-in-first-out principle.
4) batch transmission mode.
This method is used to transmit data that requires correctness. Printers, scanners, and digital cameras are usually connected to the host in this way.
Among the four data transmission modes, in addition to the equal-time transmission mode, the other three methods will attempt to resend the data when an error occurs during data transmission to ensure its accuracy.

USB interface category:

From the introduction of several commonly used mini B interfaces on devices, it is not difficult to see that, while the specifications are very complicated, an increasingly clear trend is emerging. This means that the USB interfaces on small devices will also be unified in the future development. If you analyze the current situation, we can easily see that the unified standard in the future is most likely the mini B-type 5pin interface.

Iriver MP3 didn't start with this kind of interface, and later its products became this kind of interface; Nikon's camera didn't start with this kind of interface, and later also adopted this interface; Fuji's camera didn't start with this interface, this interface is also applied to the latest products. This interface is small in size and easy to plug and unplug, especially the trapezoid design, which not only prevents mis-insertion, but also helps users blind insertion. Currently, this interface has the largest number of devices and spans various devices.

In this case, we can easily see the bright future of this interface.

Type	Type	Common Devices
Mini type-B 5pin	Mini type-B 5pin	Most devices
Mini B 4pin	Mini B 4pin	Some Olympus products, early Sony DC, Walkman
	Mini B 4pin flat	Most of Fuji's early models
Mini B 8pin	Mini B 8pin	Nikon digital cameras
	Mini B 8pin round
	Mini Type 8pin 2x4	Iriver 100 series,

For the unification of such USB interfaces, its benefits are not as great as the unification of some other specifications, but such unification can reduce the user's exclusive dependence on the original cable, it also makes coordination between devices more convenient.