명령

Question

void loop(){ 

    Serial.print("AT+CUSD=1,\"*121#\"\r"); 

    CheckOK(); 
} 

void CheckOK() { 

    while (Serial.read() != 'K'); 

    delay(100); 

} 

Answer 1

https://www.arduino.cc/en/Tutorial/StringSubstring

/* 
    String substring() 

Examples of how to use substring in a String 

created 27 July 2010, 
modified 2 Apr 2012 
by Zach Eveland 

http://www.arduino.cc/en/Tutorial/StringSubstring 

This example code is in the public domain. 
*/ 

void setup() { 
    // Open serial communications and wait for port to open: 
    Serial.begin(9600); 
    while (!Serial) { 
    ; // wait for serial port to connect. Needed for native USB port only 
    } 

    // send an intro: 
    Serial.println("\n\nString substring():"); 
    Serial.println(); 
} 

void loop() { 
    // Set up a String: 
    String stringOne = "Content-Type: text/html"; 
    Serial.println(stringOne); 

    // substring(index) looks for the substring from the index position to the end: 
    if (stringOne.substring(19) == "html") { 
    Serial.println("It's an html file"); 
    } 
    // you can also look for a substring in the middle of a string: 
    if (stringOne.substring(14, 18) == "text") { 
    Serial.println("It's a text-based file"); 
    } 

    // do nothing while true: 
    while (true); 
}