Question

Alright, I’ve googled getting a string from Serial with Arduino and I’ve had no luck even copy and pasting examples.

I’m trying to get a string from the Serial. Here’s my code:

void setup() {
    Serial.begin(9600);
    Serial.write("Power On");
}

void loop()
{
    while(!Serial.available());

    while (Serial.available() > 0) {
      Serial.write(Serial.read());
    }
    Serial.println();
}

And it’s printing out character by character.

I also tried

char* read(int len) {
  while (!Serial.available());
  char str[len];
  int i = 0;
  while (i < len) {
    str[i] = '\0';
    int inByte = Serial.read();
    Serial.println(inByte);
    if (inByte == -1) {
        return str;
    } else {
      str[i++] = inByte;
    }
  }
  return str;
}

And it returns 1 character at a time (serial.print(inByte) gives -1 every other time). Why is the Serial splitting each character?

If I enter ‘hello’ and I call serial.read() it gives a character then says there’s nothing, then gives another character and says there’s nothing.

Answer 1

I figured it out.

When you open a Serial with 9600 baud (Serial.begin(9600);), it’s reading/writing at 9600 bytes per second. That means at fastest it can get just under 10 bytes per millisecond. I don’t know what the operating speed is, but it seems like the Arduino gets alerted of and reads the first byte before the second one arrives. So, you must add a delay(1) to “wait” for another byte in the “same stream” to arrive.

String read() {
    while (!Serial.available()); //wait for user input
    //there is something in the buffer now
    String str = "";
    while (Serial.available()) {
        str += (char) Serial.read();
        delay(1); //wait for the next byte, if after this nothing has arrived it means the text was not part of the same stream entered by the user
    }
    return str;
}

You may ask, well since you’re delaying how do you know if the user is just typing very fast? You can’t avoid it here, since the Serial is essentially limited at a certain speed. However, the user must be typing virtually-impossibly-fast for two inputs to be confused as one.