Separate from Serial for digitalWrite()

[ganangxcoding]

This is my current code (Arduino Mega 2560):

#define p1 2
#define p2 3

void setup() {
 Serial.begin(9600);
 pinMode(p1, OUTPUT);
 pinMode(p2, OUTPUT);
 Serial.println("ARDUINO : CONNECTED");
}

void loop() {
 if (Serial.available()) {
  String state = Serial.readString();
  
  if (state.startsWith("LED1ON")) {
    digitalWrite(p1, HIGH);
  }
  if (state.startsWith("LED1OFF")) {
    digitalWrite(p1, LOW);
  }
  if (state.startsWith("LED2ON")) {
    digitalWrite(p2, HIGH);
  }
  if (state.startsWith("LED2OFF")) {
    digitalWrite(p2, HIGH);
  }
  // ... and next condition LED
 }
}

how can i do for multiple dynamic input serial use seperator(";") ? like : LED1ON;LED2OFF;LED3OFF;...

expacted: one time command (LED1ON;LED2OFF;...) many condition (led turn on and led 2 turn off and etc)

please, tks

[J-M-L]

I would suggest to study Serial Input Basics to handle this

[Koepel]

Welcome to the forum.

Which Arduino board do you use ? (since you use pin 1).

We don't use the Serial.readString(). Its behaviour is not well defined.
We even try to avoid the String class on a Arduino Uno.

I would like a good description of the commands that can be entered. This is where most beginners fail, so I hope that you can do this. Here are some notes to think about:

• You use the ';' as seperator, but there is no ';' after the last command ?
• What is at the end of a line ? A CarriageReturn or LineFeed or both or neither ? Suppose that you upload a file with commands, what is at the end of the lines in that case ?
• Should there be a timeout ? Suppose that you have two commands "BLINK1" and "BLINK100". If you receive "BLINK1", how long do you wait for "00" that might or might not come ?
• Do you want to add a parameter in the future ? For example blinking a led at pin 5 with 2 blinks per second: "BLINK:5:2;" or send a floating point number: "OFFSET:3.1415;". How about sending text ?
• Do you want to request data in the future ? For example requesting the version of the code: "GETVERSION;" and the Arduino will reply with "2.01.02;".

[b707]

@ganangxcoding

how can i do for multiple input serial use seperator(";") ? like : LED1ON;LED2OFF

Use a new line as separator - it solve your problem

[ruilviana]

In the setup, it is missing to initialize the serial:

"Serial.begin(XXXX); // XXXX = Serial speed. 9600, 115200,... etc...

[GolamMostafa]

@ganangxcoding

how can i do for multiple input serial use seperator(";") ? like : LED1ON;LED2OFF

@Koepel

You use the ';' as seperator, but there is no ';' after the last command ?

The command can still be parsed using strtok() function:

Sketch: (select Newline option in the Line ending box of Serial Monitor)

char myMsg[20];

void setup()
{
  Serial.begin(9600);
  pinMode(13, OUTPUT);  //LED1
  pinMode(4, OUTPUT);  //LED2
}

void loop()
{
  byte n = Serial.available();
  if (n != 0)

  {
    byte m = Serial.readBytesUntil('\n', myMsg, 20);
    myMsg[m] = '\0' ; //null charcater
    Serial.println(myMsg);
    char *token;
    token = strtok(myMsg, ";");
    if (strcmp(token, "LED1ON") == 0)
    {
      digitalWrite(13, HIGH);   //LED1 is ON, ;LED2OFF
    }
    token = strtok(NULL, ";");
    if (strcmp(token, "LED2OFF") == 0)
    {
      digitalWrite(4, LOW);   //LED2 is OFF
    }
  }
}

[StefanL38]

The Serial input basics have a demo-code in post 2

Serial Input Basics - updated

Continued from previous Post Example 3 - A more complete system The simple system in Example 2 will work well with a sympathetic human who does not try to mess it up. But if the computer or person sending the data cannot know when the Arduino is ready to receive there is a real risk that the Arduino will not know where the data starts. If you would like to explore this, change the end marker in the previous program from \n to > so that you can include the end marker in your text for illustrat…

where a start-marker and an end-marker is used to separate commands from each other.

So if you can change the character-sequence that you are sending to the arduino to look like this

<LED1ON><LED2OFF><LED3BLINK><LED4ON>

where the "<" acts as the startmarker and the "<" acts as the endmarker,
each time the end-marker is received the flag newData becomes true and you can process this one command. And then continue with reading from the serial inputbuffer.

Depending on how much characters you want to send at once you must iterate through your whole code very fast. Otherways if the number of sended characters exceeds the number the serial receive-buffer can hold some characters will get lost.

best regards Stefan

[ruilviana]

@ganangxcoding

LED1ON;LED2OFF

Try this code:

(simulated at: " https://wokwi.com/projects/371142682088743937

#define p1 2
#define p2 3

void setup() {
  Serial.begin(9600);
  pinMode(p1, OUTPUT);
  pinMode(p2, OUTPUT);
  Serial.println("ARDUINO : CONNECTED");
}

void loop() {
  if (Serial.available()) {
    String state = Serial.readString();
    //Serial.println(state);   // For debug
    state.toUpperCase();
    int msgLgt = state.length();
    //Serial.println(msgLgt); // For debug
    int semiC = state.indexOf(";");
    String firstArg = state.substring(0, semiC);
    //Serial.println(firstArg);   // For debug
    String ScndArg = state.substring(semiC + 1, msgLgt-1);
    ///Serial.println(ScndArg);   // For debug

    if (firstArg == "LED1ON") {
      digitalWrite(p1, HIGH);
    }
    if (firstArg == "LED1OFF") {
      digitalWrite(p1, LOW);
    }
    if (ScndArg == "LED2ON") {
      digitalWrite(p2, HIGH);
    }
    if (ScndArg == "LED2OFF") {
      digitalWrite(p2, LOW);
    }
    // ... and next condition LED
  }
}