The difference between MCU serial communication and parallel communication and the understanding of UART

If we need to start from a MCU Send a piece of data to another MCU, We can choose two ways of communication , Serial communication or parallel communication .

If the data we want to send is digital 198 Convert to binary , Namely 11000110, If serial communication protocol is used , We only need a data line to send data in bit order , The communication distance can range from a few meters to thousands of meters , Parallel communication protocols can also be used , We need eight data lines to send data directly and in parallel .

Because parallel data cannot carry clock information , To ensure consistent signals , Additional clock signal lines are required , And the communication speed is fast , But the corresponding line cost is also higher , The anti-interference ability is also worse , Therefore, the communication distance is very limited .

When we use MCU When communicating , Serial protocols often have simple peripherals 、 Low cost and long communication distance , So it's more popular .

Our commonly used serial protocols are Sbus,PPM,USB,RS232,Morse Code,JTAG,UART,I2C,CAN,SPI,MIDI etc. , Even Morse code is serial communication . Depending on the clock used , We can divide serial communication into synchronous communication and asynchronous communication .

That we use a lot I2C and SPI It's all synchronous communication , Both sides of synchronous communication need to use a clock with the same frequency , The receiver needs to be ready to receive data at all times , Only need assistance bit The string is used as the start and stop identification , So the transmission efficiency is high , You can also communicate one to many .

The typical representative of asynchronous communication is serial port UART. Both sides of asynchronous communication use their own clocks , The receiving method realizes information synchronization by identifying the start bit and end bit in the data packet , Therefore, the data efficiency is low , Only one-to-one communication .

Let's first look at our commonly used serial communication , Three wires are needed , Send data line TX, Receiving data line RX And reference GND You can communicate .

Before communication, both parties should know the baud rate of communication 、 Data length 、 Start bit and stop bit , For example, we need to send 198 This number is converted into binary to 11000110, We can load the data to be sent into data bits , When communicating , We also need a start bit and an end bit .

We usually use high signal to indicate that communication stops , Because in this way, there will be no communication error when the signal is interfered . When the receiver detects that the signal changes from high to low , It means to start communication , You can start reading data .

We also need to configure a parameter , It's baud rate , Our commonly used baud rate is 9600 Porter per second , It means sending every second 9600 A symbol , The length of each symbol is one divided by 9600 be equal to 104 Microsecond .

But in practical applications , When we detect that the data start bit starts reading data , Usually postponed 52 Read data in microseconds , Because the initial data may be unstable , After that, what the receiver has to do is every 104 Collect data every microsecond , Until the eight digit data is read, the data stop bit is read , Even if we use other baud rates to send different data , We also need to read the start bit and stop bit in the same way .

Like to help collect some praise , Thank you for your support and encouragement ！

Learn SCM , I'm serious about Warwick North , Children's shoes can come to me if they have any questions , Reply to Lin Bei in time to get very practical dry goods , I will be very satisfied if I can help you grow ！ Okay , That's all for this issue , See you next time ！

Hua Weilin North