STM32开发笔记63: 在LwIP中不使用MicroLIB

单片机型号：STM32F407VGT6

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文章STM32开发笔记62: 使用MicroLIB介绍了microLIB的使用方法，如果在项目中使用LwIP的话，默认是使用microLIB的，如果不勾选microLIB选项，则程序不能够正常运行，其主要原因在于LwIP使用了microLIB提供的标准输入和输出函数。但是，非常遗憾的是microLIB不支持C++，如果在应用程序中希望使用C++进行程序设计，则不能勾选microLIB，否则在链接的时候会出现问题，本文提供解决这一问题的方法。

不勾选microLIB，keil将使用标准C库函数进行链接，这就需要我们提供相应的低层支持才可以。ARM公司提供了相应的模版，我们可以通过http://infocenter.arm.com/help/topic/com.arm.doc.faqs/attached/3844/retarget.c找到该文件。然后将其加入到keil项目中，仔细分析这个文件可以看出，其只需要我们完成2个函数即可，程序如下。我在这里将其映射到了UART1。

/*
 * UART prototype functions
 */
char UART_read(void)
{
	return 0;
}

void UART_write(char ch)
{
	HAL_UART_Transmit(&huart1, (uint8_t *)&ch, 1, 10);
}

下面，我给出完整的程序，如果希望使用，将其直接拷贝即可。

/*
 * Copyright (C) ARM Limited, 2006. All rights reserved.
 * 
 * This is a retargeted I/O example which implements the functions required
 * for communication through an UART. The implementation relies on two UART
 * functions which the user must provide (UART_write and UART_read) for 
 * sending and receiving single characters to and from the UART.
 *
 * See the "rt_sys.h" header file for complete function descriptions.
 */

#include 
#include "main.h"

#ifdef __cplusplus
extern "C" {
#endif

#define DEFAULT_HANDLE 0x100;

extern UART_HandleTypeDef huart1;

/*
 * UART prototype functions
 */
char UART_read(void)
{
	return 0;
}

void UART_write(char ch)
{
	HAL_UART_Transmit(&huart1, (uint8_t *)&ch, 1, 10);
}

/*
 * These names are special strings which will be recognized by 
 * _sys_open and will cause it to return the standard I/O handles, instead
 * of opening a real file.
 */
const char __stdin_name[] ="STDIN";
const char __stdout_name[]="STDOUT";
const char __stderr_name[]="STDERR";

/*
 * Open a file. May return -1 if the file failed to open. We do not require
 * this function to do anything. Simply return a dummy handle.
 */
FILEHANDLE _sys_open(const char * name, int openmode)
{
    return DEFAULT_HANDLE;  
}

/*
 * Close a file. Should return 0 on success or a negative value on error.
 * Not required in this implementation. Always return success.
 */
int _sys_close(FILEHANDLE fh)
{
    return 0; //return success
}

/*
 * Write to a file. Returns 0 on success, negative on error, and the number
 * of characters _not_ written on partial success. This implementation sends
 * a buffer of size 'len' to the UART.
 */
int _sys_write(FILEHANDLE fh, const unsigned char * buf,
               unsigned len, int mode)
{
    int i;
    for(i=0;i1)
            {
                // Delete character on terminal
                UART_write('\b');
                UART_write(' ');
                UART_write('\b');         
                
                // Update position in buffer
                pos-=2;   
            }
            else if (pos>0) pos--; // Backspace pressed, empty buffer
        }
        else UART_write(buf[pos-1]); // Echo normal char to terminal
        
        
    }while(buf[pos-1] != '\r');
    
    buf[pos]= '\0'; // Ensure Null termination

    return 0;       
}

/*
 * Writes a character to the output channel. This function is used
 * for last-resort error message output.
 */
void _ttywrch(int ch)
{
    // Convert correctly for endianness change
    char ench=ch;
    
    UART_write(ench);
}

/*
 * Return non-zero if the argument file is connected to a terminal.
 */
int _sys_istty(FILEHANDLE fh)
{
    return 1; // no interactive device present
}

/*
 * Move the file position to a given offset from the file start.
 * Returns >=0 on success, <0 on failure. Seeking is not supported for the 
 * UART.
 */
int _sys_seek(FILEHANDLE fh, long pos)
{
    return -1; // error
}

/*
 * Flush any OS buffers associated with fh, ensuring that the file
 * is up to date on disk. Result is >=0 if OK, negative for an
 * error.
 */
int _sys_ensure(FILEHANDLE fh)
{
    return 0; // success
}

/*
 * Return the current length of a file, or <0 if an error occurred.
 * _sys_flen is allowed to reposition the file pointer (so Unix can
 * implement it with a single lseek, for example), since it is only
 * called when processing SEEK_END relative fseeks, and therefore a
 * call to _sys_flen is always followed by a call to _sys_seek.
 */
long _sys_flen(FILEHANDLE fh)
{
    return 0;
}

/*
 * Return the name for temporary file number sig in the buffer
 * name. Returns 0 on failure. maxlen is the maximum name length
 * allowed.
 */
int _sys_tmpnam(char * name, int sig, unsigned maxlen)
{
    return 0; // fail, not supported
}

/*
 * Terminate the program, passing a return code back to the user.
 * This function may not return.
 */
void _sys_exit(int returncode)
{
    while(1) {};
}

#ifdef __cplusplus
}
#endif

 

 

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