It consists of ground wire, power wire, D+ and D- respectively. D+ and D- are differential input lines, which use a voltage of 3.3V (note that it is different from the 5V level of CMOS), while the power line and ground wire can provide the equipment with a voltage of 5V and a maximum current of 500MA.

Data format of USB:

Like others, USB data is composed of binary number strings. First, the number string constitutes a domain (there are seven kinds), then the domain constitutes a package, then the package constitutes a transaction (in, OUT, SETUP), and finally the transaction constitutes a transmission (interrupt transmission, parallel transmission, batch transmission and control transmission).

Coding scheme of USB data line;

USB uses non-return-to-zero inversion to transmit data. When the differential data on the transmission line is input 0, it is inverted, and when 1 is input, the original value is maintained. In order to ensure the accuracy of signal transmission, when sending data packets on USB bus, the transmission device will insert a bit (that is, insert a 0 after every 6 consecutive 1 s in the data stream), thus forcing the NRZI code to change.

Extended data:

Interface definition

Red, white, green and black are standard wiring colors, corresponding to pins 1, 2, 3 and 4 respectively.

These four wires are 1- power supply 2- data 3- data 4- power supply.

The general arrangement is: red, white, green and black from left to right.

Definition:

Red-USB power supply is marked with the words-VCC, power supply, 5V and 5VSB.

White-USB data line (negative electrode)-data-,USBD-, PD-, USBDT+

Green-USB cable (positive electrode)-Data+,USBD+, PD+, USBDT+

Black-Ground-GND Ground

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