I'm developing on android with bluetooth LTE, I can send hex codes, but I send one code at time, so I need to send many informations in this way, how can I recognize a string and save the datas inside an array to parse it later?

Here is my sketch:

 char c=' ';
 String inString,one,check;
 char inData[11];
 char inChar;
 int counter=0;
 bool started = false;
 bool ended = false;
 byte index;

boolean NL = true;
const int LED1 = 6;
const int LED2 = 7;
const int LED3 = 2;
const int LED4 = 3;
const int LED5 = 4;
const int LED6 = 5;

void setup() {
    Serial.print("Sketch:   ");   Serial.println(__FILE__);
    Serial.print("Uploaded: ");   Serial.println(__DATE__);
    Serial.println(" ");

    Serial.println("BTserial started at 9600");

    pinMode(LED1, OUTPUT);
    pinMode(LED2, OUTPUT);
    pinMode(LED3, OUTPUT);
    pinMode(LED4, OUTPUT);
    pinMode(LED5, OUTPUT);
    pinMode(LED6, OUTPUT);


void loop() {

  if (BTserial.available()>0)
      Serial.print("bts: ");
      c = BTserial.read();
      check =  String(c, HEX); 

        while (BTserial.available()>0){

            inChar = BTserial.read();
            if(check != "0xfff3")
                inData[index] = inChar;
        for (int i=0;i<=11;i++){
          one =  String(inData[i], HEX); 
          Serial.print(i);Serial.print(": ");Serial.println(one);


             // Serial.write(c);
              digitalWrite(LED1, !digitalRead(LED1));
              digitalWrite(LED2, !digitalRead(LED2));
              digitalWrite(LED3, !digitalRead(LED3));
              digitalWrite(LED4, !digitalRead(LED4));
             // Serial.write(c);
              digitalWrite(LED5, !digitalRead(LED5));
             // Serial.write(c);
              digitalWrite(LED6, !digitalRead(LED6));

Without the loop I can read all the single datas, but for my job it's not enough, to recognize the data applications I send a "sample string" to recognize the type of informations I want to send.


1 Answer 1


i think i solved in some way, i send always the same codes at the start and at the end of the datas, so i can racognize the end and then i parse the first element of the destination array. tell me what you think abou, if it could help someone else:

 if (BTserial.available()>0)
  c = BTserial.read();
  check =  String(c, HEX);      
  if(check!="fff3"){              // i always start wit an fff3
  inData[index] = c;
  else if(check=="fff3"){         //end of data
  index=0;                        //reset the index for the next set of data
  if(String(inData[1], HEX)=="ffbc"){
    Serial.println("read the next 10 data of the array");
    }else if(String(inData[1], HEX)=="11"){
    Serial.println("turn on led 1");

    // for more operations use a switch/case over the if

  • 1
    Why are you using a string to check for the start/end data? You can simply use the hex representation: if(c == 0xfff3). And I'm a bit confused, that you have a 4-digit hex code for one read operation. If you use the SoftwareSerial library as your BTserial object, a call of the read() function returns one byte at a time, so it would be a 2-digit hex code
    – chrisl
    Commented Feb 4, 2018 at 14:39
  • hi, i'm using the bluetooth nativescript plugin, i don't know why but if i send a character after 9 arduino receives ffxx, (if i send 0xaa, it sends 0xffaa). when i made the first experiments i couldnt understnd the set of characters to parse, so i found the string. for the btserial i use altsoftserial
    – peppeg85
    Commented Feb 5, 2018 at 6:48

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