The microcontroller does not support the printf function, so implement several common serial port printing functions

Under keil C51 or iar for c8051 compiler:

1. int occupies two bytes: -32768~+32767

2. Long occupies four bytes: -2147483648~+2147483647

3. float occupies four bytes: 3.40E+38 ~ +3.40E+38

4. Double occupies 8 bytes range: -1.79E+308 ~ +1.79E+308

51 MCU is a general term for all MCUs compatible with Intel 8031 ​​instruction system. The ancestor of this series of MCUs is Intel's 8004 MCU. Later, with the development of Flash ROM technology, 8004 MCU has made great progress and become one of the most widely used 8-bit MCUs.

In stand-alone development, serial port debugging or collecting real-time data of various data types often requires the use of printf() function redirection, but the performance of printf() is poor for microcontrollers with scarce resources. For the convenience of future work, several commonly used printing functions are recorded.

For non-recursive implementation, see another blog http://www.cnblogs.com/02xiaoma/archive/2012/06/22/2558618.html

However, the void printflt(double flt) in the blog cannot correctly print the format of 0 after the decimal point, such as 1.000123, 1.01 1.001, 1.0001, etc.

Non-recursive

Integer printing

void printInterger(int integer)
{
    unsigned char isnegative = 0,len = 0, intstr[10]={''};
    if(integer < 0)
    {
        isnegative = 1;
        integer = 0 - integer;
    }
    if (integer == 0)
        intstr[len++] = '0';
    while (integer)
    {
        intstr[len++] = (integer % 10) + '0';
        integer = integer / 10;
    }
    if(isnegative)
        intstr[len++] = '-';
    //Note the data type of k. Use k >= 0; as the end condition. k is a signed type. If it is an unsigned type, the k value rolls back to the maximum value
    for(len = len; len > 0; len--)
    {
        //printf("%c", intstr[len-1]);
        UartSend(UART1,&intstr[len-1],1);
}}

Floating point numbers

void printFlt(float flt,int len)
{
    int integer;
    integer = (int)flt;
    printHex(integer);
    //printf(".");
    UartSend(UART1,".",1);
 
    flt = flt - integer;
    //while(flt&&(len--))
    while(flt)
    {
        flt = flt*10;
        integer = (int)flt + '0';
        flt = flt - integer;
        //printf("%c",integer);
        UartSend(UART1,&integer,1);
    }
}

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Recently, some students are troubled by the problem of how to use the serial port of the microcontroller to output and display on the host computer serial port assistant during the learning process of 51 single-chip microcomputer. In fact, many development environments support the use of the most commonly used printf function in C language, and Keil is no exception. It is not only the most commonly used STC89C52, but also other 51 series microcontrollers under Keil, such as STC12, STC15, etc. The specific steps are as follows:

Create an empty project in Keil, add a source file, such as main.c, paste the following code, compile to generate a hex file, and download it to the microcontroller.

        It should be noted that: 1. The stdio.h header file needs to be included 2. TI = 1 is required in the serial port initialization function;

        Without further ado, let's get straight to the code:

#include
#include
 
void InitUART(void)//Use timer 1 as the serial port baud rate generator
{
    TH1 = 0xFD; //Crystal oscillator 11.0592mhz baud rate set to 9600
    TL1 = TH1;
    TMOD |= 0x20; //Timer 1 mode 2
    SCON = 0x50; //Serial port receive enable
    ES = 1; //Serial port interrupt enable
    TR1 = 1; //Timer 1 enable
    TI = 1; //Send interrupt flag, must be set
}
//Millisecond delay function
void delay_ms(unsigned int t)
{
    unsigned char a,b;
    while(t--)
    {
      for(b=102;b>0;b--)
      for(a=3;a>0;a--);
    }
}
 
void main()
{
    InitUART(); //Initialize the serial port
    EA = 1; //Open the general interruptwhile
    (1)
    {
        delay_ms(500);
        printf("Hello World!n");//Serial port print result
    }
}