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Large Decryption Of USB Data Line Structure
Apr 14, 2018

The most common function of the USB data line is data transmission and charging, and other structures are rarely known. The following gives you a more comprehensive knowledge of the USB data line structure: USB data line structure: ground line, power line, D+, D, respectively - Four lines, D+ and D- are differential input lines. It uses a 3.3V voltage (note that unlike CMOS 5V levels), the power and ground lines can provide 5V to the device, and the maximum current 500MA (can be set in the programming, as to the hardware implementation mechanism, do not ignore it).

USB data format: As with others, USB data consists of binary digit strings. First, the digit string constitutes the domain (there are seven types). The domain is reconstructed into packets. The packet then constitutes the transaction (IN, OUT, SETUP). Make up the transmission (interruption transmission, parallel transmission, batch transmission and control transmission).

USB data line encoding scheme: USB uses non-return to negate to transfer data, when the differential data on the transmission line is input, it is negated. When input 1, the original value is kept, in order to ensure the accuracy of signal transmission, when the USB When a packet is sent on the bus, the transmitting device performs a bit insertion operation (ie, inserts a 0 after every six consecutive 1s in the data stream), forcing the NRZI code to change.

There is data sent in the USB data line is sent from low to high.