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Arduino reads a string from Serial

#include <stdio.h>

#define LED 13

void setup() {
  pinMode(LED, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int i;
  char command[5];
  for (i = 0; i < 4; i++) {
    command[i] = Serial.read();
  }
  command[4] = '\0';

  Serial.println(command);

  if (strcmp(command, "AAAA") == 0) {
    digitalWrite(LED, HIGH);
    Serial.println("LED13 is ON");
  } else if (strcmp(command, "BBBB") == 0) {
    digitalWrite(LED, LOW);
    Serial.println("LED13 is OFF");
  }
}

I am trying to read a 4 character string with Arduino Serial, and when this AAAA turns on the LED, when it is BBBB, turn off the serial port.

However, when I enter "AAAA", it reads "AAAÿ" with a lot of "ÿ" along the way.

I think I read everything correctly, but it doesn’t work so well, any idea what I am doing wrong?

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4 answers
#define numberOfBytes 4
char command[numberOfBytes];

    void serialRX() {
      while (Serial.available() > numberOfBytes) {
        if (Serial.read() == 0x00) { //send a 0 before your string as a start byte
          for (byte i=0; i<numberOfBytes; i++)
            command[i] = Serial.read();
        }
      }
    }
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String txtMsg = "";  
char s;

void loop() {
    while (serial.available() > 0) {
        s=(char)serial.read();
        if (s == '\n') {
            if(txtMsg=="HIGH") {  digitalWrite(13, HIGH);  }
            if(txtMsg=="LOW")  {  digitalWrite(13, LOW);   }
            // Serial.println(txtMsg); 
            txtMsg = "";  
        } else {  
            txtMsg +=s; 
        }
    }
}
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, - . , read() -1. Serial.available(), .

+1

"ÿ", char. , uart. , , . , .

In addition, this way of waiting for characters is not the best way, since it blocks the main loop.

Here is what I do in my programs:

String command;

void loop()
{
    if(readCommand())
    {
        parseCommand();
        Serial.println(command);
        command = "";
    }
}

void parseCommand()
{
  //Parse command here
}

int readCommand() {
    char c;
    if(Serial.available() > 0)
    {
        c = Serial.read();
        if(c != '\n')
        {       
            command += c;
            return false;
        }
        else
            return true;

    }
}
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