Can a string be sent over serial connection to open a swtch using c++ and an arduino?

Question

Question Summary:

It works, but on my specific case I am get into problems due to data encoding. Data is sent through the arduino as "coin" but its printed output in my console application is "2". Then I have the issue of sending the string "1234" from my console application, and not being able to receive it in the arduino. I think the data is being set as a different encoding so that the statement is nos looking for the right information. It is that simple and that complicated. (oh stackoverflow!)

Serial port is open and baud rate is set

Arduino code snippets:

Serial.println('coin');

if( Serial.readString() == "1234"); <<<--- how can i relax this condition as i did in the example below. (it does work on the Serial monitor but not on the software, is it an encoding situation?)

VS code snippets:

SerialPort sp = (SerialPort)sender;

string indata = sp.ReadExisting();

if (indata.Contains("coin"))   <<<---  it is a relaxed contains condition, **works** in my case, since I dont really know excaclty what it is receiving.

SerialPort.Write("1234"); (how do I make sure it receives the characters i send be it ANSI hex or whatever.

thanks for your help.

Start of Regular post

Good afternoon,

I have arduino code:

int ledPin = 13;
const int coinInt = 0;
int incomingByte = 0;

#define RELAY_ON 1
#define RELAY_OFF 0
#define Relay_2  7

int waittime;
volatile int coinsValue = 00;
volatile int coinsChange = 0;       //A Coin has been inserted flag

void setup()   {
  digitalWrite(Relay_2, RELAY_ON);
  pinMode(Relay_2, OUTPUT);  
  delay(1000);

  Serial.begin(9600);                
  attachInterrupt(coinInt, coinInserted, RISING);   //If coinInt goes HIGH (a Pulse), call the coinInserted function
}

void coinInserted()  {
  coinsValue = coinsValue + 01; 
  coinsChange = 1;  //Flag
}

void loop() {
  if(coinsChange == 1)   
  {
    coinsChange = 0;   

   if(coinsValue >= 50)   {
      Serial.println('coininsertion');
      coinsValue = 0;
      digitalWrite(Relay_2, RELAY_OFF);
      digitalWrite(ledPin, HIGH);    
  }
         if (Serial.available() > 0) {
                incomingByte = Serial.read();
                delay(250);
                digitalWrite(ledPin, LOW);
                digitalWrite(Relay_2, RELAY_ON);

   }                
  }
}

and c# console application code:

using System;
using System.IO.Ports;
using System.Diagnostics;
using System.Threading;


class PortDataReceived
{
    public static void Main()
    {
        SerialPort mySerialPort = new SerialPort("COM3");

        mySerialPort.BaudRate = 9600;
        mySerialPort.Parity = Parity.None;
        mySerialPort.StopBits = StopBits.One;
        mySerialPort.DataBits = 8;
        mySerialPort.Handshake = Handshake.None;
        mySerialPort.RtsEnable = true;

        mySerialPort.DataReceived += new SerialDataReceivedEventHandler(DataReceivedHandler);

        mySerialPort.Open();


      Console.WriteLine("Press a key to continue...");
      Console.WriteLine();
      Console.ReadKey();
      mySerialPort.Close();
    }

    private static void DataReceivedHandler(
                        object sender,
                        SerialDataReceivedEventArgs e)
    {

        SerialPort sp = (SerialPort)sender;
        string indata = sp.ReadExisting();
   //     Thread.Sleep(100);
       // Console.Write(indata);
        Thread.Sleep(100);
        if (indata.Contains("coininsertion"))
        {
            Thread.Sleep(100);
            //Process.Start(@"C:\\Users\laptop\Documents\rb_software\print.ahk");
           Process process = new Process();
            // Configure the process using the StartInfo properties.
           process.StartInfo.FileName = @"C:\\Users\laptop\Documents\rb_software\print.ahk";
            //process.StartInfo.Arguments = "-n";
            //process.StartInfo.WindowStyle = ProcessWindowStyle.Maximized;
           process.Start();
           Thread.Sleep(100);
           process.WaitForExit();
           Thread.Sleep(1000);// Waits here for the process to exit.
           sp.Write("a");

        }

      Console.Write(indata);

    }
}

A relay closes in the arduino code at the very end:

void loop() {
  if(coinsChange == 1)   
  {
    coinsChange = 0;   

   if(coinsValue >= 50)   {
      Serial.println('coininsertion');
      coinsValue = 0;
      digitalWrite(Relay_2, RELAY_OFF);
      digitalWrite(ledPin, HIGH);    
  }
         if (Serial.available() > 0) {
                incomingByte = Serial.read();
                delay(250);
                digitalWrite(ledPin, LOW);
                digitalWrite(Relay_2, RELAY_ON);

   }                
  }
}

Or at least its supposed to close. Since I sent a character over serial connection in my c++ code near the end:

  process.WaitForExit();
               Thread.Sleep(1000);// Waits here for the process to exit.
               sp.Write("a");

Anyhow, I would appreciate if someone could tell me why it is not closing the switch. Namely turning Relay_2 "ON".

That is all. thanks again.

Answer 1

Main question: is it working if you use Serial Monitor to send that control character?

Notes for Arduino code (sometimes "WTFs"):

• ledPin, LOW; in setup() and also no pinMode for this pin
• coinsChange must be volatile too as it's set by ISR handler and checked in loop
• Forget about: 00, 01, these values are considered as octal. For these values it's not a problem, but if you use something like 0012 it will be 10 in decimal!!
• I've never seen comments under the commands they belong. You can place them to line before, to same line (after), but it's highly confusing to have them on line under. Lots of them are commenting obvious things - like: Serial.begin(9600); //Start Serial Communication
• Wrong indentation makes this code hard to read. And it's few lines.
• waittime is set only once, never used again.
• Are you sure coin inserted signal is debounced? If not, it'll be counting lot of pulses for one coin insertion.
• Why are you so inconsistent with pin numbers and other constants? Once it's int, once const int, once #define...
• if (incomingByte == '97') pick one: == 97 or == 'a' but never '97' as it's a nonsense for a char.

Btw: that C++ code is actually C#

EDIT: you've fixed just few things. But most important no. For example indentation. Also ' is for ONE character. If you want string, you HAVE TO use "some string". And you definitely wan't serial processing outside of block if(coinsChange == 1). After som tidy up:

const int  ledPin = 1;
const int Relay_2 = 7;
const int coinInt = 0; // coin external interrupt no

int  incomingByte = 0;

#define RELAY_ON 1
#define RELAY_OFF 0

int waittime = 1000;

// Volatile as this variable changes any time the Interrupt is triggered
volatile int  coinsValue = 0;  // Set the coinsValue to a Volatile float
volatile int coinsChange = 0;  // A Coin has been inserted flag

void setup()
{
  pinMode(ledPin, OUTPUT);
  digitalWrite(ledPin, LOW);

  // -------( Initialize Pins so relays are inactive at reset)----
  digitalWrite(Relay_2, RELAY_ON);
  pinMode(Relay_2, OUTPUT);

  delay(1000);

  Serial.begin(9600);

  // Attach coinInt to Interrupt Pin 0 (Digital Pin 2). Pin 3 = Interrpt Pin 1.
  // If coinInt goes HIGH (a Pulse), call the coinInserted function
  // An attachInterrupt will always trigger, even if your using delays
  attachInterrupt(coinInt, coinInserted, RISING);
}

void coinInserted()  // The function that is called every time it recieves a pulse
{
  ++coinsValue;     // As we set the Pulse to represent 5p or 5c we add this to the coinsValue
  coinsChange = 1;  // Flag that there has been a coin inserted
}

void loop()
{
  if(coinsChange == 1) // check if a coin has been Inserted
  {
    coinsChange = 0;   // unflag that a coin has been inserted
    if(coinsValue >= 50)
    {
      Serial.println("coininsertion");
      coinsValue = 0;
      digitalWrite(Relay_2, RELAY_OFF);
      digitalWrite(ledPin, HIGH);
    }
  }

  if (Serial.available() > 0) {
    incomingByte = Serial.read();
    delay(250);

    if (incomingByte == 'a') {
      digitalWrite(ledPin, LOW);
      digitalWrite(Relay_2, RELAY_ON);
    }                
  }
}

Answer 2

I think for transmitting and receiving Strings, It is better to use String class in arduino. try Serial.readString()

https://www.arduino.cc/en/Serial/ReadString

here is my sample code for checking a password from RX pin

void loop() {
  if (Serial.available() > 0) {  // if the data came

data=Serial.readString();


if( data == "1234") {
  data="";
   digitalWrite(LED, HIGH); // if 0, switch LED on
   Serial.println("LED ON. Press 0 to LED OFF!");
}
 if(data=="0000"){
 data="";
   digitalWrite(LED, LOW);  // if 1, switch LED Off
   Serial.println("LED OFF. Press 1 to LED ON!");  // print message
}
}

I hope it helps you.