Comprehensive Analysis of Microcontroller Serial Communication Protocols

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Comprehensive Analysis of Microcontroller Serial Communication Protocols

In the field of embedded systems, achieving communication between devices is a very important aspect. Serial communication protocols are undoubtedly a powerful means to achieve this goal. Today, let’s delve into several commonly used serial communication protocols in microcontrollers.

Basic Concepts of Serial Communication

As the name suggests, serial communication means transmitting data bit by bit in sequence. In contrast, parallel communication transmits multiple bits at once. Although parallel communication is more efficient, it requires more hardware lines and is more costly, so serial communication is more commonly used in microcontrollers and embedded systems.

Common Serial Protocols

The commonly used serial communication protocols in microcontrollers mainly include the following:

1. UART

Full name: Universal Asynchronous Receiver-Transmitter. As its name implies, communication using UART is asynchronous. This means that there is no shared clock signal between the sender and receiver. Instead, they must first negotiate the baud rate before data transmission can occur. UART supports full-duplex communication, allowing simultaneous sending and receiving of data.

The typical application scenarios for UART include: serial connection between microcontrollers and PCs, wireless communication between microcontrollers and Bluetooth/WiFi modules, etc.

1. SPI

Full name: Serial Peripheral Interface. Unlike UART, the clock for SPI is provided by the master device, allowing multiple slave devices to communicate with the master device, forming a master-slave structure. Data is transmitted in full-duplex mode between the master device and the slave devices. SPI is commonly used to connect external memory or sensors.

1. I2C

Full name: Inter-Integrated Circuit. I2C requires only two data lines (SDA, SCL) to complete communication, characterized by minimal line occupation and good flexibility. Multiple slave devices can be connected to the I2C bus, distinguished by device addresses. I2C is most commonly used to connect EEPROM, real-time clock chips, etc.

Next, let’s take the most commonly used UART as an example to perform practical operations.

UART Hardware Circuit

To use UART on a microcontroller, we need to connect the following pins:

• TXD – Transmit Data
• RXD – Receive Data
• GND – Common Ground
• VCC – Power Supply

Be sure to pull up or pull down the TXD and RXD pins according to the chip manual’s specifications.

UART Communication Code

In terms of program code, we need to perform the following configurations:

1. Initialize the UART control register, configuring parameters such as baud rate, data bits, stop bits, parity bits, etc.
2. Set up send and receive interrupts.
3. Write functions for sending and receiving data.

For example, using the 8051 microcontroller and Keil software, a simple UART data sending function can be implemented as follows:

#include <reg51.h>

sfr TMOD = 0x89;           // Timer mode control register
sfr SCON = 0x98;           // Serial control register
sfr SBUF = 0x99;           // Serial data register
sfr PCON = 0x87;           // Power control register

void InitUART(void)
{
    TMOD = 0x20;           // Set Timer 1 to mode 2
    SCON = 0x50;           // Set serial mode 1, 8-bit data, variable baud rate
    PCON |= 0x80;          // Enable baud rate doubling
    TH1 = 0xFD;            // Set baud rate to 9600
    TL1 = 0xFD;
    TR1 = 1;               // Start Timer 1
    ES = 0;                // Disable serial interrupt
}

void SendByte(unsigned char Byte)
{
    SBUF = Byte;           // Place data into send buffer
    while (!TI);           // Wait for send to complete
    TI = 0;               // Clear send complete flag
}

This is just a basic example; you can add more functionalities based on your needs, such as multi-byte sending, data packing, and unpacking, etc.

UART Application Scenarios

By mastering UART communication, we can connect the microcontroller with many other devices, such as:

• Connecting to a computer for data transmission and program downloading.
• Integrating WiFi/Bluetooth modules for remote wireless control.
• Connecting to GPS modules to obtain location information.
• Integrating serial screens to create human-machine interaction interfaces.
• ……

In summary, UART serial communication is an indispensable skill in the development of microcontrollers. I hope that through this article’s explanation, you have grasped the basic principles and application methods of UART. The next step is for you to practice and personally experience the joy of serial communication.

If you have any questions during your learning and practice, feel free to ask, and I will answer them one by one. Oli give!