Problem a: transmission line structure of USB is how?

　　Answer: Dongguan Apple data line wholesale tell you, transmission line USB are respectively composed of wire, power line, D+, D- four lines, D+ and D- aredifferential input line, it is using the 3.3V voltage (note Oh, unlike the 5V level of CMOS), and the power line and ground can provide the 5V voltage to theequipment, the maximum current of 500MA (can be set in the programming, as forhardware realization mechanism, do not ignore it.).

　　Question two: how data is transferred in the USB transmission line inside

　　Answer two: Dongguan Apple data line wholesale tell you, data transfer in the USB line is from low to high transmission.

　　Question three: USB coding scheme?

　　Answer three: Dongguan Apple data line wholesale tell you, USB uses a non return to zero counter to transmit data, when the transmission line differential data input 0 when taking anti -, input 1 when you keep the original value, in order to ensure the accuracy of signal transmission, when sending a packet on the USB bus,transmission equipment to place the insert operation (i.e., data flows in each of 6 consecutive 1 after insertion of a 0), thereby forcing NRZI code changes.

　　Question four: USB data format is?

　　Answer four: like any other, USB data is composed of a binary digit string consisting of the first digit string, constitute the domain (seven kinds), domain then form package, package and then constitute a transaction (IN, OUT, SETUP), the transaction finally form a transmission (interrupt transmission, parallel transmissionand mass transmission and transfer of control).