PC -> arduino serial communication

Stoil · January 21, 2019, 7:28pm

Hello,
I have a c# app that's constantly sending integers 0-255 as strings to Arduino.
I want a LED to light up when the value is above a certain threshold.

Arduino code:

void setup() {
  pinMode(5, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  digitalWrite(5, LOW);
   while (Serial.available() > 0) {
    int inChar = Serial.read();
    if (inChar > 230){
        digitalWrite(5, HIGH); 
      }
    if (inChar == '\n') {
      if (inChar > 230){
        digitalWrite(5, HIGH);       
      }
    }
  }
}

I have the c# app simultaneously writing in a .txt as a sort of a "debug". The .txt contains multiple rows with 230+ values.
The LED doesn't light up.
However, if I upload this code:

void setup() {
  pinMode(5, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  digitalWrite(5, LOW);
   while (Serial.available() > 0) {
    digitalWrite(5, HIGH);
  }
}

It lights up once I start the app that sends data.
I cannot open the serial monitor because it seems the c# app is eating it up.
Suggestions ?

Stoil · January 21, 2019, 7:44pm

I understand what you're saying but I cannot open the Serial monitor, it says it's busy.
If I could see what's coming in, I could easily code it.

Stoil · January 21, 2019, 8:56pm

Hi again,
I went over the guide but still feel hopeless without actually seeing the received values, since I cannot even modify the code in any direction.
So I took the example for numbers using atoi() but now it always goes inside the if().
Probably the number is a pointer to an integer or something.

Stoil · January 21, 2019, 9:01pm

Like I said, it is sending 0-255 numbers as a string.
And the .txt contains the right values (0-255) on a new line each.
edit: I'm assuming atoi(theinput) returns a pointer so it's always > my threshold.

Stoil · January 21, 2019, 9:06pm

I'm assuming SerialPort.WriteLine(string s) does send a new line, hence the name.

Stoil · January 21, 2019, 9:41pm

Yes, this is what the documentation says. The problem, in my opinion, lies somewhere else.
The only way the code can get inside the if() is if the value is a pointer, I don't see what else could be it.
I am not sure what atoi() returns in my scenario.

sumguy · January 21, 2019, 10:12pm

If all you are sending is one single value between zero and 255 then instead of sending ASCII strings you could instead send the value as a byte.

  byte[] sdata=new byte[1];

        private void button1_Click_1(object sender, EventArgs e)
        {
            sdata[0] = 231;
            myport.Write(sdata, 0, 1);
        }


 private void button2_Click(object sender, EventArgs e)
        {
            sdata[0] = 229;
            myport.Write(sdata, 0, 1);
        }

The above is hard coded values of 231 and 229 to show the LED toggle on and off with the following Arduino code, which is your code slightly mopdified.

void setup() {
  pinMode(5, OUTPUT);
  Serial.begin(9600);
  digitalWrite(5, LOW);
  
}

void loop() {

   while (Serial.available() > 0) {
   int inChar = Serial.read();
    
    if (inChar > 230){
        digitalWrite(5, HIGH); 
      }
    if (inChar<230) {
     
        digitalWrite(5, LOW);       
      
    }
  }
}

If you still want to do this using an ASCII string then take a closer look at the link Delta_G provided (Serial Input Basics) and study example 5

Robin2 · January 21, 2019, 10:40pm

Have a look at the examples in Serial Input Basics - simple reliable ways to receive data. There is also a parse example to illustrate how to extract numbers from the received text.

The technique in the 3rd example will be the most reliable.

You can send data in a compatible format with code like this (or the equivalent in any other programming language)

Serial.print('<'); // start marker
Serial.print(value1);
Serial.print(','); // comma separator
Serial.print(value2);
Serial.println('>'); // end marker

It makes debugging much easier if you send data in human readable form. I would only send binary data if it was the only way to achieve the required performance.

...R

Stoil · January 22, 2019, 8:38am

Like I said before, the program is sending strings on a new line each. The string consists of numbers 0-255.

void recvWithEndMarker() {
** static byte ndx = 0;**
** char endMarker = '\n';**
** char rc;**

** if (Serial.available() > 0) {**
** rc = Serial.read();**
** if (rc != endMarker) {**
** receivedChars[ndx] = rc;**
** ndx++;**
** if (ndx >= numChars) {**
** ndx = numChars - 1;**
** }**
** }**
** else {**
** receivedChars[ndx] = '\0'; // terminate the string**
** ndx = 0;**

** }**
** }**
** dataNumber = 0; **
** dataNumber = atoi(receivedChars);**
}

Isn't this supposed to turn, let's say 505151, to 233 ?

Robin2 · January 22, 2019, 9:06am

Stoil:
Isn't this supposed to turn, let's say 505151, to 233 ?

The way I wrote the code it is not. My recvWithEndMarker() function is only intended to receive the data. Make another function elsewhere something like this and call it from loop()

void convertCharsToInt() {
  if (newData == true) {
         dataNumber = atoi(receivedChars); 
         newData = false;
   }
}

...R

Stoil · January 22, 2019, 9:13am

Is this not exactly what I am doing ? The method is in the loop. The atoi is at the end.

Robin2 · January 22, 2019, 9:58am

Stoil:
Is this not exactly what I am doing ? The method is in the loop. The atoi is at the end.

I have no idea. Does it work for you?

Does my system work for you?

...R

Stoil · January 22, 2019, 10:33am

No, it currently does not work. I'm not new to receiving data from serial, it's just that I can always open the serial monitor and modify the code accordingly, but this time..

Whandall · January 22, 2019, 10:58am

Stoil:
No, it currently does not work. I'm not new to receiving data from serial,
it's just that I can always open the serial monitor and modify the code accordingly,
but this time..

... you should make the c# code print out anything it receives from serial, so you can have debug output.

Robin2 · January 22, 2019, 12:37pm

Stoil:
No, it currently does not work.

Referring to my Reply #19 does your use of the word "it" refer to my first question or my second question?

If it refers to my second question then please post the complete program you have tried so I can see exactly what you have done.

If it refers to my first question then try what I implied in my second question.

...R

Stoil · January 24, 2019, 5:44pm

Here's the complete code:

const byte numChars = 32;
char receivedChars[numChars]; 
void setup() {
  pinMode(5, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  recvWithEndMarker();
  
  digitalWrite(5, LOW);
 
}

void recvWithEndMarker() {
    static byte ndx = 0;
    char endMarker = '\n';
    char rc;
    
    while (Serial.available() > 0) {
        rc = Serial.read();

        if (rc != endMarker) {
            receivedChars[ndx] = rc;
         
            ndx++;
            if (ndx >= numChars) {
                ndx = numChars - 1;
            }
        }
        else {
            receivedChars[ndx] = '\0'; // terminate the string
            ndx = 0;
        }
    }
    int num = atoi(receivedChars);
    if (num > 254){
      digitalWrite(5, HIGH);
    }
}

I repeat for the nth time, I'm sending strings from my c# app:

           foreach(var r in _spectrumdata)
            {
                port.WriteLine(r.ToString());
            }

With the current code it always enters the if(num>254);

edit: weirdly or not, I tried writing to the EEPROM the received data with and without atoi() and it just receives it receives "178" without atoi() and "2" with atoi().

Stoil · January 24, 2019, 6:16pm

Delta_G:
How do you know it is getting into that if statement? If it does and sets the pin HIGH, then the very next line in loop sets it right back to LOW. So how would you ever see that without a scope?

The atoi() is outside of the loop. Isn't the end of the loop the full data ?
WriteLine appends a new line. Do I really need a start marker if all the data I receive is of the type and has an end marker ?
I know because I tried with a lower number such as 1, which basically means it would flicker non stop.

Stoil · January 24, 2019, 7:06pm

Like I said, if I put 0 in the if, it flickers like mad.
Where would you like me to put the atoi() in this case ? I do have an end marker tho.
I'm trying to make some leds light up when there's a beat while music is playing.

Stoil · January 24, 2019, 8:07pm

Friend, I have literally copied the OPs code for reading numbers and added my if statement.

const byte numChars = 32;
char receivedChars[numChars]; 

boolean newData = false;

int dataNumber = 0;
void setup() {
  pinMode(5, OUTPUT);
  Serial.begin(9600);
}

void loop() {
recvWithEndMarker();
    showNewNumber();
  digitalWrite(5, LOW);  
}



void recvWithEndMarker() {
    static byte ndx = 0;
    char endMarker = '\n';
    char rc;
    
    if (Serial.available() > 0) {
        rc = Serial.read();

        if (rc != endMarker) {
            receivedChars[ndx] = rc;
            ndx++;
            if (ndx >= numChars) {
                ndx = numChars - 1;
            }
        }
        else {
            receivedChars[ndx] = '\0'; // terminate the string
            ndx = 0;
            newData = true;
        }
    }
}

void showNewNumber() {
    if (newData == true) {
        dataNumber = 0;             // new for this version
        dataNumber = atoi(receivedChars);   // new for this version
        if (dataNumber > 230)
        {
          digitalWrite(5, HIGH);
       
        }
        newData = false;
    }
}

This results in nonstop ON LED
edit: fixed. Now it works.

Thanks everybody for the patience, excuse my lack of knowledge in arduino, I'm just a poor C#er.

Robin2 · January 24, 2019, 9:39pm

Stoil:
, I'm just a poor C#er.

That doesn't matter. The Arduino does not use C#

...R

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