Using an Arduino as a remote

Projects General Guidance
1

Hi,
I am trying to connect raspberry Pi to arduino using usb serial which it works.Now i am trying to make the arduino take a number from serial,decode it and then using if statments send a IR signal to my tv(the IR part works).the problem is i cant get it to decode i have even setup a small debug info for serial monitor but it wont take the command.Please i am desperate dont say me use google,this is a noob question etc. I will tell you any aditional info you need here is the code:

char rx_byte = 0;
String code = "";
const int led = 10;

void setup() {
  Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
  pinMode(led, OUTPUT);
}

void loop() {
  //Reads the command code
  if (Serial.available() > 0) {
    rx_byte = Serial.read();
  
       if (rx_byte != '\n') {//moves the characters to a string
       code += rx_byte;
       Serial.print("Byte ");
       Serial.println(rx_byte);
       Serial.print("String ");
       Serial.println(code);
  
           //Looks up which command the control code responds to
           if (code == 1) {
           digitalWrite(led, HIGH);
           }
           else if(code == 2) {
           digitalWrite(led, LOW);
           delay(100);
         }
       }//end char search
    }//end main if
}//end loop
2

Your code has this:

code += rx_byte;

You need to look at the ASCII character table and there you will see the rx_byte you got has a value of 30 if a zero or a value of 31, if a one. You need to convert the ASCII character to a numeric value. If you will only, ever get a number, subtract 30 from rx_byte then add to code.

Paul

3 
 if (code == 1) {

If code is a String then shouldn't that be:

if (code == "1") {

Since you do not clear the code String, each new entry will be added to the String.

This seems to work:

char rx_byte = 0;
String code = "";  
const int led = 10;

void setup()
{
   Serial.begin(115200); // opens serial port, sets data rate to 9600 bps
   pinMode(led, OUTPUT);
}

void loop()
{
   //Reads the command code
   if (Serial.available() > 0)
   {
      code = ""; // ******  clear the code variable so entries don't accumulate  ***********
      rx_byte = Serial.read();

      if (rx_byte != '\n')  //moves the characters to a string
      {
         code += rx_byte;
         Serial.print("Byte ");
         Serial.println(rx_byte);
         Serial.print("String ");
         Serial.println(code);

         //Looks up which command the control code responds to
         if (code == "1")
         {
            Serial.println("got 1");
            digitalWrite(led, HIGH);
         }
         else if (code == "2")
         {
            Serial.println("got 2");
            digitalWrite(led, LOW);
            delay(100);
         }
      }//end char search
   }//end main if
}//end loop

For reliable non-blocking serial reception that does not use the problematic String class see the serial input basics tutorial.

4

thanks to everyone,to clearyfy it will be only numbers coming in but the problem is there will be numbers higer than 9 which arduino dosent like

5

Couple of things

  • why not just use the pi or Arduino on their own ?
  • I think the pi serial is at 3.3v , the Arduino at 5v . You need level shifting between the two , if you haven’t done this .

The serial bit is the same whatever the device , the Arduino does love numbers over 9 in the same way too.

6

hammy:
Couple of things

  • why not just use the pi or Arduino on their own ?
  • I think the pi serial is at 3.3v , the Arduino at 5v . You need level shifting between the two , if you haven’t done this .

The serial bit is the same whatever the device , the Arduino does love numbers over 9 in the same way too.

Hi i want to use the pi for the processing because i plan to run multiple of arduinos and i dont trust connecting them over wifi or bluethout soo this is the easistes hardwiring i can do i i also love using Node red for my automation.I am also 15 yr old and my parents get annoyed when i ask them to get me something of ebay and it gets a lot more expensive because there is no electronics store near me to buy a level shiffter(which i know about).What I meant is that the standard Serial.read dosent like a 2 decimal number like 10 or higher atleast that is my understanding of it.

7

Look at the second example in the serial input basics tutorial to see how to receive a string (not String) with more than one character. With that example you can receive all of the characters of the string then act on the complete string.