STM32 study notes (eight) --- communication basics

Basic knowledge of communication

First, the classification of communication

1. According to data transfer mode sub

   a serial communication: According to the data bits in the form of one bit of data transmission

   b parallel communication: transmission 16, 32 and 64 using one or more data lines

2. According to data communication direction points

   You can simultaneously send and receive data between the same time, two devices: a full-duplex.

   Can not send and receive data between the same time, two devices: b half-duplex.

   c simplex: any time, only a single direction of communication

3. According to data synchronized in the modes of

   a synchronous communication: the sender and receiver use the same clock signal lines will be coordinated at two sides of the driving clock signal, synchronous data

   b asynchronous communication: do not use a clock signal synchronized.

Second, the communication speed

Communication rate : typically bit rate (bitrate) indicates, i.e., the number of bits transmitted per second, bits per second (bit / s)

Baud Rate (Baudrate): indicate how many per second transmission symbol

Symbol : communication same time interval used to represent a binary number notation, such signals are referred to as symbols.

Comparative baud and bit rates :

As is common in the communications transmission, represented by numbers 0 0V, 5V represents a number 1, then one symbol may represent two states 0 and 1, the one symbol equal to a binary bit, the baud rate at this time the size of the bit concordance rate; if transmission in the communication, there is 0V, 2V, 4V and 6V, respectively, represent the binary number 00, 01, 10, 11, then each symbol can represent four states, i.e. two binary bits, the symbol the number is half the number of bits of binary, this time the baud rate is half the bit rate.

Third, the communication protocol

In computer science, the most complex problems can all be simplified by stratification.

Physical Layer : a communication system having predetermined mechanical characteristics, electronic functional parts, to ensure the transmission of the original data in the physical media.

Protocol layer : logical communication requirements, unified send and receive both data packing, unpacking standards.