Serial Communication - Using printf Function

For boards without emulators, the serial port is a very good debugging tool. You can set the variables you need to observe

Send it to the PC through the serial port for subsequent analysis and debugging. Here we mainly introduce how to use the serial port in Keil C

Debugger.

The program code is as follows:

#include

#include

void serial_init(void);

void main()

{

    serial_init();

    while(1)

    {

        printf("Hello,Serial Port\n";

    }

}

void serial_init(void) //Serial port initialization function

{

   TMOD = 0x20; //T1 working mode 1, used to set the baud rate

   TH1 = 0xF3; //Baud rate 4800Bps, 12MHz crystal

   TL1  = 0xF3;

   PCON |= 0x80; //SMOD = 1, baud rate doubled

   SCON = 0x50; //Allow sending and receiving

   ES = 0; //Disable serial port interrupt

   IF = 1;

   TR1  = 1;

}

It should be noted that the microcontroller crystal oscillator is 12MHz (otherwise the baud rate setting will be incorrect).

Create a project, compile, enter the debugging interface, select "Peripheraals"-"Serial" in the menu, and you will see the serial port settings.

In the interface, we can see that before the serial port is initialized, the parameters of the serial port are all 0x00, and other options are not set.
Press F10 to enter single-step debugging and execute the serial_init function. We can see that the serial port has been initialized and the baud rate is 4806. After the serial port is initialized, we can use the printf function to output the information we need (note that the stdio.h file is required). Here, we only output a simple string information example. Select the menu "View"-"Serial Window #1", you can see a blank
area, which is where the serial port information is displayed. Execute the printf function and you can see the words "Hello, Serial Port" printed on the screen.

When debugging a program on actual hardware, we can use this method to observe the values ​​of related variables and debug the program when we encounter problems. Once the program is OK, we can remove the printf function.