Convert serial.read() into a useable string using Arduino?

Question

I\'m using two Arduinos to sent plain text strings to each other using newsoftserial and an RF transceiver.

Each string is perhaps 20-30 characters in length. How do

Answer 1

Many great answers, here is my 2 cents with exact functionality as requested in the question.

Plus it should be a bit easier to read and debug.

Code is tested up to 128 chars of input.

Tested on Arduino uno r3 (Arduino IDE 1.6.8)

Functionality:

• Turns Arduino onboard led (pin 13) on or off using serial command input.

Commands:

• LED.ON
• LED.OFF

Note: Remember to change baud rate based on your board speed.

// Turns Arduino onboard led (pin 13) on or off using serial command input.

// Pin 13, a LED connected on most Arduino boards.
int const LED = 13;

// Serial Input Variables
int intLoopCounter = 0;
String strSerialInput = "";

// the setup routine runs once when you press reset:
void setup() 
{
  // initialize the digital pin as an output.
  pinMode(LED, OUTPUT);

  // initialize serial port
  Serial.begin(250000); // CHANGE BAUD RATE based on the board speed.

  // initialized
  Serial.println("Initialized.");
}

// the loop routine runs over and over again forever:
void loop() 
{
  // Slow down a bit. 
  // Note: This may have to be increased for longer strings or increase the iteration in GetPossibleSerialData() function.
  delay(1);
  CheckAndExecuteSerialCommand();  
}

void CheckAndExecuteSerialCommand()
{
  //Get Data from Serial
  String serialData = GetPossibleSerialData();
  bool commandAccepted = false;

  if (serialData.startsWith("LED.ON"))
  {
    commandAccepted = true;
    digitalWrite(LED, HIGH);   // turn the LED on (HIGH is the voltage level)
  }
  else if  (serialData.startsWith("LED.OFF"))
  {
    commandAccepted = true;
    digitalWrite(LED, LOW);    // turn the LED off by making the voltage LOW
  }
  else if (serialData != "")
  {
    Serial.println();
    Serial.println("*** Command Failed ***");
    Serial.println("\t" + serialData);
    Serial.println();
    Serial.println();
    Serial.println("*** Invalid Command ***");
    Serial.println();
    Serial.println("Try:");
    Serial.println("\tLED.ON");
    Serial.println("\tLED.OFF");
    Serial.println();
  }

  if (commandAccepted)
  {
    Serial.println();
    Serial.println("*** Command Executed ***");
    Serial.println("\t" + serialData);
    Serial.println();
  }
}

String GetPossibleSerialData()
{
  String retVal;
  int iteration = 10; // 10 times the time it takes to do the main loop
  if (strSerialInput.length() > 0)
  {
    // Print the retreived string after looping 10(iteration) ex times
    if (intLoopCounter > strSerialInput.length() + iteration)
    {
        retVal = strSerialInput;
        strSerialInput = "";
        intLoopCounter = 0;
    } 
    intLoopCounter++;
  }

  return retVal;
}

void serialEvent()
{  
  while (Serial.available())
  {    
    strSerialInput.concat((char) Serial.read());
  } 
}

Answer 2

This would be way easier:

 char data [21];
 int number_of_bytes_received;

 if(Serial.available() > 0)
 {
   number_of_bytes_received = Serial.readBytesUntil (13,data,20); // read bytes (max. 20) from buffer, untill <CR> (13). store bytes in data. count the bytes recieved.
   data[number_of_bytes_received] = 0; // add a 0 terminator to the char array
 } 

 bool result = strcmp (data, "whatever");
 // strcmp returns 0; if inputs match.
 // http://en.cppreference.com/w/c/string/byte/strcmp


 if (result == 0)
 {
   Serial.println("data matches whatever");
 } 
 else 
 {
   Serial.println("data does not match whatever");
 }

Answer 3

Use string append operator on the serial.read(). It works better than string.concat()

char r;
string mystring = "";

while(serial.available()) 
   {
    r = serial.read();
    mystring = mystring + r; 
   }

After you are done saving the stream in a string(mystring, in this case), use SubString functions to extract what you are looking for.