What Is a USB Analyzer?
A USB Analyzer is a device inserted between a host and peripheral devices communicating on the USB bus to capture data packets flowing on the bus and analyze the bus according to the USB protocol.
Before the USB bus was standardized, the interface between a PC and peripheral devices differed from device to device, requiring separate keyboards, mice, printers, etc., which was very complicated and expensive. This was because it was necessary to prepare circuits and driver software to drive the bus according to each interface standard.
With the release of the USB bus protocol, peripheral devices need only support the USB bus protocol as an interface.
Uses for USB Analyzers
USB is now used in PCs, tablets, smartphones, cell phones, digital cameras, printers, PC peripherals, and more recently, cars. Some devices have several USB ports.
The USB terminals on each device are available in several shapes due to the size of the device and its limitations.
1. Type-A
The Type-A connector has a rectangular insertion opening when viewed from the outside. This type is a standard connector and is usually used for PCs.
2. Type-C
Type-C can be used without concern for the direction in which it is plugged in and is compatible with the USB 3.1 standard, which supports high-speed transfers. Recently, as notebook PCs and smartphones have become smaller, this type of connector has also become lighter and smaller.
3. Type-B, MicroUSB
Type-B is used for relatively large devices such as printers. In addition, there are MicroUSB used for smartphones and MiniUSB used for digital cameras.
USB Analyzer is a device for analyzing data transmission on the USB bus for devices with the above USB terminals.
Principle of USB Analyzer
The USB bus allows up to 5 repeaters (hubs) to be connected to one host, and up to 127 peripheral devices can be connected.
The USB Analyzer analyzes the bus according to the protocols defined for the USB bus described above. In USB, communication between the host and peripheral devices is based on packets, the smallest unit of which is a chunk of bit strings.
The communication of a data string consisting of multiple packets is called a transaction. This is the basis of data communication, and there are four transfer modes of communication over this physical communication: control transfer, interrupt transfer, bulk transfer, and isochronous transfer.
Types of USB Analyzers
USB Analyzers come in a wide variety of sizes and functions. In addition to the common stationary type that is always connected to a PC, the following two types are typical types:
1. PC-Less Type
This type allows measurement results to be checked without a PC. Some models are equipped with a display monitor for visual confirmation, a simple printout function to print out the results, and an SD card or other storage device to transfer data to a PC at a later time.
2. Compact Type
It is lightweight and ultra-compact enough to fit in a breast pocket. It is portable and USB bus-powered, so no AC power supply or adapter is required. Considering that it can be used in any environment, bundled software is often available for various operating systems such as Windows, Linux, and MacOSX.
Additional Information on USB Analyzers
Advantages of Communication Protocols
Consider the case where a mouse is connected as a USB peripheral device. Generally, when a mouse is connected to a PC as a new device, you are not asked to install a device driver.
This is because the USB peripheral device takes a procedure to inform the host of its identity immediately after connecting to the PC and initiating communication. Based on this information from the peripheral device, the host retrieves and configures the standard device driver it holds internally.
This eliminates the need to install a device driver each time a new USB peripheral device is connected.