Arduino 串口接受字符串操作

对于Arduino串口部分的使用，多少有点不太方便，虽然官方提供了调用的函数，但是使用不够灵活，如下就对Arduino串口实现字符串的操作做个总结；

（1）自定义函数操作方式：

/*使用自定函数，将字符转化为字符串，再进行操作*/

String comdata = "";//声明字符串变量

void setup() 
{
  Serial.begin(9600);      //设定的波特率
}

void loop() 
{
   while (Serial.available() > 0)  
    {
        comdata += char(Serial.read());
        delay(2);
    }
    
   if (comdata.length() > 0)
    {
       Serial.println(comdata);
       comdata = "";
    }
}

此方法使用自定函数实现了字符到字符串的转换再进行操作，使用起来还不错，推荐大家使用。

（2）第二种，简单暴力的方法，采用库函数Serial.readString()；

void setup() 
{
  Serial.begin(9600);      //设定的波特率
}

void loop() 
{
  String rx_buffer;
  rx_buffer=Serial.readString();
  Serial.print(rx_buffer);
}

此方法使用简单暴力，但是有个确定，官方库函数默认的参数使得读取串口操作必须要阻塞1s的时间，实时性较差；

在这里，提供一种修改方法：

在Arduino IDE 安装路径下找到 stream.h 文件修改参数

①文件路径：D:\Arduino1_8_5\hardware\arduino\avr\cores\arduino

②找到文件 stream.h，修改参数：Stream() {_timeout=200;}，红色数值单位为毫秒，根据需要修改然后保存编译即可生效；

附 stream.h 文件内容（突出显示要修改的地方：Stream() {_timeout=200;}）：

/*
  Stream.h - base class for character-based streams.
  Copyright (c) 2010 David A. Mellis.  All right reserved.

  This library is free software; you can redistribute it and/or
  modify it under the terms of the GNU Lesser General Public
  License as published by the Free Software Foundation; either
  version 2.1 of the License, or (at your option) any later version.

  This library is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  Lesser General Public License for more details.

  You should have received a copy of the GNU Lesser General Public
  License along with this library; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

  parsing functions based on TextFinder library by Michael Margolis
*/

#ifndef Stream_h
#define Stream_h

#include <inttypes.h>
#include "Print.h"

// compatability macros for testing
/*
#define   getInt()            parseInt()
#define   getInt(ignore)    parseInt(ignore)
#define   getFloat()          parseFloat()
#define   getFloat(ignore)  parseFloat(ignore)
#define   getString( pre_string, post_string, buffer, length)
readBytesBetween( pre_string, terminator, buffer, length)
*/

// This enumeration provides the lookahead options for parseInt(), parseFloat()
// The rules set out here are used until either the first valid character is found
// or a time out occurs due to lack of input.
enum LookaheadMode{
    SKIP_ALL,       // All invalid characters are ignored.
    SKIP_NONE,      // Nothing is skipped, and the stream is not touched unless the first waiting character is valid.
    SKIP_WHITESPACE // Only tabs, spaces, line feeds & carriage returns are skipped.
};

#define NO_IGNORE_CHAR  '\x01' // a char not found in a valid ASCII numeric field

class Stream : public Print
{
  protected:
    unsigned long _timeout;      // number of milliseconds to wait for the next char before aborting timed read
    unsigned long _startMillis;  // used for timeout measurement
    int timedRead();    // read stream with timeout
    int timedPeek();    // peek stream with timeout
    int peekNextDigit(LookaheadMode lookahead, bool detectDecimal); // returns the next numeric digit in the stream or -1 if timeout

  public:
    virtual int available() = 0;
    virtual int read() = 0;
    virtual int peek() = 0;

    Stream() {_timeout=200;}

// parsing methods

  void setTimeout(unsigned long timeout);  // sets maximum milliseconds to wait for stream data, default is 1 second
  unsigned long getTimeout(void) { return _timeout; }
  
  bool find(char *target);   // reads data from the stream until the target string is found
  bool find(uint8_t *target) { return find ((char *)target); }
  // returns true if target string is found, false if timed out (see setTimeout)

  bool find(char *target, size_t length);   // reads data from the stream until the target string of given length is found
  bool find(uint8_t *target, size_t length) { return find ((char *)target, length); }
  // returns true if target string is found, false if timed out

  bool find(char target) { return find (&target, 1); }

  bool findUntil(char *target, char *terminator);   // as find but search ends if the terminator string is found
  bool findUntil(uint8_t *target, char *terminator) { return findUntil((char *)target, terminator); }

  bool findUntil(char *target, size_t targetLen, char *terminate, size_t termLen);   // as above but search ends if the terminate string is found
  bool findUntil(uint8_t *target, size_t targetLen, char *terminate, size_t termLen) {return findUntil((char *)target, targetLen, terminate, termLen); }

  long parseInt(LookaheadMode lookahead = SKIP_ALL, char ignore = NO_IGNORE_CHAR);
  // returns the first valid (long) integer value from the current position.
  // lookahead determines how parseInt looks ahead in the stream.
  // See LookaheadMode enumeration at the top of the file.
  // Lookahead is terminated by the first character that is not a valid part of an integer.
  // Once parsing commences, 'ignore' will be skipped in the stream.

  float parseFloat(LookaheadMode lookahead = SKIP_ALL, char ignore = NO_IGNORE_CHAR);
  // float version of parseInt

  size_t readBytes( char *buffer, size_t length); // read chars from stream into buffer
  size_t readBytes( uint8_t *buffer, size_t length) { return readBytes((char *)buffer, length); }
  // terminates if length characters have been read or timeout (see setTimeout)
  // returns the number of characters placed in the buffer (0 means no valid data found)

  size_t readBytesUntil( char terminator, char *buffer, size_t length); // as readBytes with terminator character
  size_t readBytesUntil( char terminator, uint8_t *buffer, size_t length) { return readBytesUntil(terminator, (char *)buffer, length); }
  // terminates if length characters have been read, timeout, or if the terminator character  detected
  // returns the number of characters placed in the buffer (0 means no valid data found)

  // Arduino String functions to be added here
  String readString();
  String readStringUntil(char terminator);

  protected:
  long parseInt(char ignore) { return parseInt(SKIP_ALL, ignore); }
  float parseFloat(char ignore) { return parseFloat(SKIP_ALL, ignore); }
  // These overload exists for compatibility with any class that has derived
  // Stream and used parseFloat/Int with a custom ignore character. To keep
  // the public API simple, these overload remains protected.

  struct MultiTarget {
    const char *str;  // string you're searching for
    size_t len;       // length of string you're searching for
    size_t index;     // index used by the search routine.
  };

  // This allows you to search for an arbitrary number of strings.
  // Returns index of the target that is found first or -1 if timeout occurs.
  int findMulti(struct MultiTarget *targets, int tCount);
};

#undef NO_IGNORE_CHAR
#endif

参考资料：http://tieba.baidu.com/p/4723699275?traceid=

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Arduino 串口接受字符串操作

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