Arduino serial communication. How to read the device response via rs232?

[m_gh21]

Hello forum,

this is my first threat on this helpful forum..

I want to send dataprotocols from my Arduino via the serial interface rs232 to the mass flow controller, get response and print it on the serial monitor .

this is an excerpt from the instruction manual

Purpose:

1. send the protocol as a HEX (array) commands to MFC (Bronkhorst)
2. receive the response as a String
3. print the response on serial monitor.

Problem

I converted the protocol to hexa and sent it to MFC, but i don't get the expected response shown on the serial monitor.

#include <SoftwareSerial.h>

SoftwareSerial m_Port(15,14); // (Rx, Tx) on arduino Mega2560

// the whole protocol is :06030401210121\r\n 
String bronkhrostProtocol = ":06030401210121"; // first part of the protocol | in hexadecimal: 3A303630333031303132313345383

int string_length;
int digitalVlaue;
String R;
String maReponse;

void setup() {
  Serial.begin(9600);
  m_Port.begin(38400);
  string_length = bronkhrostProtocol.length();
  while(!Serial) {}
}

void loop() {
Serial.println('\n');  
Serial.print("StringLen is: ");                   // just a scope to show length of the String 
Serial.println(string_length);
Serial.println('\n');

//======= Converting to hexadecimal========
//=======================================================

char char_Array [string_length];
for(int i = 0; i< string_length; i++){
 char_Array[i] = bronkhrostProtocol.charAt(i);   // store the string elements to char array
}
Serial.print("for loop ");                       // just a scope

for(int j=0; j<string_length; j++){
  
  Serial.print(char_Array[j]);                   // scope to show the array elements
  }
  Serial.println('\n');

String hex_array2 = "0D0A";                      // second part of the protocol is allready converted to hexa
char char_Array2[hex_array2.length()];

for(int f = 0; f<hex_array2.length(); f++){      //store the hex elements in array2
  char_Array2[f] = hex_array2.charAt(f);
  }
  
  for(int m = 0; m<16; m++){
   m_Port.print(char_Array[m], HEX);            // send the first part of the protocol to Mass Flow Controller in hexadecimal
  }
  
 for(int l = 0; l<5; l++){
  Serial.print(char_Array2[l], HEX);
  m_Port.print(char_Array2[l]);                // send the second part of the protocol to Mass Flow Controller in hexadecimal
  }
  Serial.println('\n');

  //========= Answer form MFC===================
  //===============expected answer is :06030201213E80\r\n
  //====================================================
R = m_Port.readStringUntil('\n'); // should read the response until '\n'
//maReponse = R.substring(0,10);
Serial.println("Answer is ");
Serial.print(R);
  
  while (true){
  }
  
}

on the serial monitor i got this

Is there any possibility to send the hexa data other than using m_Port.print(char_Array[m], HEX);?

Any thoughts on this issue shall be appreciated.
Thank you!

[anon73444976]

@m_gh21

String hex_array2 = "0D0A";                      //

Did you mean
String hex_array2 = "\r\n"; ?

Why did you make the code so complicated?

[m_gh21]

yes.. I am still a beginner in coding with arduino. thanks

[Koepel]

Let's make it easier then.

Which Arduino board do you have.
Is that a Arduino Mega 2560 ? then please don't use the SoftwareSerial, but use Serial1.

this is a text string (an array of characters):

char outtext[] = ":06030401210121\r\n"

this is how you send it every second

void loop()
{
  Serial1.write( outtext);
  delay( 1000);
}

You could read the response after half a second:

void loop()
{
  Serial1.write( outtext);
  delay( 500);
 
  while( Serial1.available() > 0)
  {
    Serial.write( (byte) Serial1.read());
  }

  delay( 500);
}

I followed the KISS rule.

If you don't get any response, how do you know that your wiring is okay ? How do you know that your message gets to the MFC ?
Can you test the device with a computer ? Do you have a scope or logic analyzer ?

Please tell us what kind of device it is. We want to read the documentation ourselves.

[ADDED] Found the documentation of your screendump. It is 917027-Manual-RS232-interface.pdf from bronkhorst.com.

[m_gh21]

thanks for your answer!

It is the Arduino Mega2560 and the device is the Bronkhorst MASS-STREAM (D-6321-DR).. The wiring should be correct, because i have alternately wired tx with rx between RS232 and Arduino board..
Here is also the instruction manual of the mass flow controller
917027-Manual-RS232-interface.pdf (1,8 MB)

[Koepel]

How do you know that your MFC has node 3 ?
You could try to send a message to all nodes. I think the old fashioned sprintf function is the best to build the string.

char buffer[20];
int length = 6;
int node = 3;
int command = 4;
sprintf( buffer, ":%02d%02d%02d0x210121\r\n", length, node, command);

But before you do that, use my example to make the most simple sketch that is possible and show us that super simple sketch.

[jremington]

@Koepel

sprintf( buffer, ":%02d%02d%02d0x210121\r\n", length, node, command);

This won't work, according to the device manual. It states to use ASCII Hex representation for all data bytes. The transmission is terminated by a single CR or '\r' although I imagine that '\n' might be ignored.

From the manual:

All bytes (except the initial and termination character) are converted from 1 binary byte to 2 hexadecimal bytes in ASCII representation. Example: binary data byte 0x2A --> hexadecimal ASCII characters 0x32, 0x41.

I suggest %X formatting (but do not know what might be intended by the "210121" bit).

sprintf( buffer, ":%02X%02X%02X210121\r", length, node, command);

[Koepel]

There is

• existing RS232-HOST ASCII protocol
• ProPar enhanced binary protocol
• Communication messages between ProPar interfaces

They three different things. Now I'm confused

[sterretje]

@m_gh21, your topic has been moved to a more suitabable location on the forum.

Pins 14 and 15 on the Mega are hardware serial ports (Serial3); although it might not solve your problem, I suggest that you get rid of SoftwareSerial and use Serial3 everywhere instead of m_Port.