Read char over serial [SOLVED]

Hi, im trying to send an array of char over serial to my arduino uno. My arry would be something like 12345. Im trying to only read the first character of the array. That’s what i got so far.

void setup()


void loop(){
  char ch;
  String value;
  char inData [20];
  char inChar;
  byte index;


     if(index < 19) // One less than the size of the array
          inChar =; // Read a character
         inData[index] = inChar; // Store it
         index++; // Increment where to write next
          inData[index] = '\0'; // Null terminate the string

But the arduino is sending the value like this:


and when i change the




there’s nothing printing. I know its a noobie problem and the answer is not very difficult. What am i doing wrong ?

Thank you for helping the little beginner i am !

djosimd !

Every time through loop() your index will be reset to 0. You wait for at least one character to exist in the serial buffer, then read it in to element "index" (which is 0), then increment index. If there is only one character (which is often the case - one character arrives at a time into the serial buffer), then loop() will finish. Next time through to get the second character, index is 0 again.

uhm, i see, so is there a simple way to just store the whole array at the same time ? I could be able to work with the value stored in a string. Im on my wait out right now but, ill try to change my if(index<19) for some for loop. Would that be working ?

I juste want to be able to do somethings depending on the value of a char depending on is position in the array

If you are expecting a specific number of characters you can wait for that number of characters to be available in the serial buffer. Otherwise you will need to watch for a terminating character, like \r

You cannot read a whole array at one time, you have to read it character by character and put each in the next array position as you have tried to do. As has been pointed out, your problem is that you keep setting index back to zero on each pass through loop().

Reading Serial input works much slower that the repeat speed of the loop() function so by the time the next character has been read index has been set back to zero.

Very simple string capture.

// zoomkat 7-30-11 serial I/O string test
// type a string in serial monitor. then send or enter
// for IDE 0019 and later

String readString;

void setup() {
  Serial.println("serial test 0021"); // so I can keep track of what is loaded

void loop() {

  while (Serial.available()) {
    delay(2);  //delay to allow byte to arrive in input buffer
    char c =;
    readString += c;

  if (readString.length() >0) {


Nice as a starting point, but there is absolutely no reason to ever use the String class for such a basic operation.

Nice as a starting point, but there is absolutely no reason to ever use the String class for such a basic operation.

So post your working code. 8)

OK, if you insist, but I’d rather the OP worked it out for themselves…

#define MAX_MESSAGE 30

void setup()

void loop()
  static char buffer[MAX_MESSAGE];
  static unsigned char index = 0;
  char inch;
  while (Serial.available() > 0) {
    inch =;
    if (inch == '\r') {
      Serial.print("You entered: ");
      buffer[0] = 0;
      index = 0;
    } else {        
      if (index < MAX_MESSAGE-1) {
        buffer[index++] = inch;
        buffer[index] = 0;

… make sure you use the serial monitor with line endings set to “carriage return”.

Thank you majenko !!! I modified your code to fit my needs and its working great !!! and its light and easy to understand !! Thank you very much !!!