Arduino：Serial.find（char）无法正常工作

Question

Firstly, setup: Arduino IDE 1.5.7 beta, Nano v3.0

In short, my goal: use Serial.find() to wait for both standard EOL characters (both ASCII 13, CR, and ASCII 10, NL) to be found in the serial buffer, before proceeding with the following code.

my (problematic/shortened) code:

char charCr = 13;
char charNl = 10;

void loop(){
    do_stuff; 
    foo(); 
    do_other_stuff;}

void foo() 
{
      while (true)
      {
          if (Serial.find(bar1) && Serial.find(bar2))
          {
              break; // EOL characters found
          }
          delay(1); // wait to receive EOL
      }; 
}

OK, so two separate problems with what goes in bar1 and bar2

If the bars are respectively charCr and charNl then the code doesn't compile whilst complaining:

error: call of overloaded 'find(char&)' is ambiguous
note: candidates are:
In file included from C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino/HardwareSerial.h:29:0,
from C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino/Arduino.h:221

finds a near match, which, I believe is the correct definition of find, as Serial inhereits it from Stream

C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino/Stream.h:59:8: note: bool Stream::find(char*) <near match>
bool find(char *target);   // reads data from the stream until the target string is found

But then also complains the char input should be a pointer (char*):

C:\Program Files (x86)\Arduino\hardware\arduino\avr\cores\arduino/Stream.h:59:8: note:   no known conversion for argument 1 from 'char' to 'char*'

The documentation I've read on Serial.find() and Stream.find() suggests that char should not be a pointer, just to pass the char value. Regardless, if bar1 and bar2 are referenced as &charCr and &charNl the code compiles fine, but the conditional is never met, and I know that I am sending both EOL characters, as confirmed by different means and debugging code.

So... what's going wrong with my code?

Answer 1

The documentation on the website is misleading because they say string but the function prototype is (char). A string is a variable length character array. A char is a single character. When in doubt, always believe the function declaration in the header file (.H). From Stream.h:

bool find(char *target);   // reads data from the stream until the target string is found
// 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
// returns true if target string is found, false if timed out

With those in mind, there are two ways forward. Search single characters:

// method as you started - accepts terminators in either order
char charCr = 13;
char charNl = 10;

if (Serial.find(&charCr, 1) && Serial.find(&charNl, 1))

or string form:

char termseq1[] = {13, 10, 0};
char termseq2[] = {10, 13, 0};

if (Serial.find(termseq1) || Serial.find(termseq2))