如何统一从串口接收数据？

Question

I want to establish a full duplex connection between the microcontroller(ARM Stm32F4) and the program made by Unity software via c#. This connection must be made through the serial port. I need a two-way connection between these two parts. At first the sent data from the program (made in unity software) can send command to the microcontroller(ARM Stm32F4), then the microcontroller must check the received data and verifying finishing commands to the Unity software If the data is correct, send the next data to the program. My problem is that my program, which is made by the unity, does not receive finished data that sent from the microcontroller.

How can I have full duplex connection?

*
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;
using System.IO.Ports;
using System.IO;
using UnityEditor;
using SerialPortUtility;
using System;
public class gcode : MonoBehaviour
{
    string str;
    string str1;
    public SerialPort sina;
    public InputField sendgcode;
    public InputField plusoffset;
    public InputField minusoffset;
    public InputField lenghtoffset;
    public InputField counter;
    public Button plus_inc;
    public Button plus_dec;
    public Button minus_inc;
    public Button minus_dec;
    public Button lenght_inc;
    public Button lenght_dec;
    string board;
    
    Array[] inserial;
    //int resend = 0;
    // Start is called before the first frame update
    void Start()
    {
        sina = new SerialPort("com1", 115200);
        sina.ReadTimeout = 100;
        
        sina.Open();
        sina.DtrEnable = true;
    }
    // Update is called once per frame
    void Update()
    {
        //sina.Close();
            //str = sina.ReadLine();
            //sendgcode.text = str;
        
    }
    public void sendserial()
    {
        
        str = sendgcode.text;
        TextWriter a40 = new StreamWriter("c:\\1.txt");
        a40.WriteLine(str);
        a40.Close();
        str = "";
        TextWriter a41 = new StreamWriter("c:\\2.txt");
        TextWriter a43 = new StreamWriter("c:\\3.txt");
        TextWriter a22 = new StreamWriter("c:\\22.txt");
        TextWriter plus = new StreamWriter("c:\\p.txt");
        TextWriter minus = new StreamWriter("c:\\m.txt");
        TextWriter lenght = new StreamWriter("c:\\t.txt");
        System.IO.StreamReader file = new System.IO.StreamReader("c:\\1.txt");
        while ((str = file.ReadLine()) != null)
        {
            str1 = str.Replace(" ", "");
            str1 = str1.Replace("L", "\r\n");
            str1 = str1.Replace("A", "\r\n");
            str1 = str1.Replace("S", "");
            a41.WriteLine(str1);
        }
        a41.WriteLine("S");
        a41.Close();
        file.Close();
        System.IO.StreamReader file22 = new System.IO.StreamReader("c:\\2.txt");
        while ((str = file22.ReadLine()) != "S")
        {
            if (str.Length >= 1) { a22.WriteLine(str); }
        }
        a22.WriteLine("S");
        a22.Close();
        file22.Close();
        System.IO.StreamReader file1 = new System.IO.StreamReader("c:\\22.txt");
        while ((str = file1.ReadLine()) != "S")
        {
            int idx = str.IndexOf('-');
            if (idx >= 0)
            {
                if (str.Length == 2)
                {
                    str = str.Replace("-", "-00");
                    a43.WriteLine(str);
                }
                else if (str.Length == 3)
                {
                    str = str.Replace("-", "-0");
                    a43.WriteLine(str);
                }
                else
                {
                    a43.WriteLine(str);
                }
            }
            else if (str.Length == 1)
            {
                a43.WriteLine("00" + str);
            }
            else if (str.Length == 2)
            {
                a43.WriteLine("0" + str);
            }
            else
            {
                a43.WriteLine(str);
            }
        }
        a43.WriteLine("S");
        a43.Close();
        file1.Close();
        str1 = null;
        int c = 0;
        System.IO.StreamReader file2 = new System.IO.StreamReader("c:\\3.txt");
        while ((str = file2.ReadLine()) != "S")
        {
            if (str.Length > 2)
            {
                str1 = str1 + str;                          //read line by line to 4 line
            }
            c++;
            if (c == 4)                                     //end read 4 lines
            {
                c = 0;
                int n = 0;
                str1 = "#" + str1;
                int sp;
                
                do
                {
                    sina.WriteLine(str1);
                    board = sina.ReadExisting();
                    Debug.Log(board);               
                }
                while (board != str1);
                sina.WriteLine("$");
                str1 = null;
            }
             
            
        }
        /*
        System.Threading.Thread.Sleep(1000);
        sina.WriteLine(str1);                               //send last line of gcode     
        file2.Close();
        System.Threading.Thread.Sleep(1000);
        sina.WriteLine("p" + plusoffset.text);
        System.Threading.Thread.Sleep(1000);
        sina.WriteLine("m" + minusoffset.text);
        System.Threading.Thread.Sleep(1000);
        sina.WriteLine("t" + lenghtoffset.text);
        System.Threading.Thread.Sleep(1000);
        System.IO.StreamReader filecrc = new System.IO.StreamReader("c:\\3.txt");
        int crc = 0;
        int s1;
        int Poffset = 0;
        int Moffset = 0;
        int Toffset = 0;
        int Ecount = 0;
        while ((str = filecrc.ReadLine()) != "S")
        {
            int.TryParse(str, out s1);
            crc = crc + s1;
        }
        filecrc.Close();
        int.TryParse(plusoffset.text, out Poffset);
        int.TryParse(minusoffset.text, out Moffset);
        int.TryParse(lenghtoffset.text, out Toffset);
        int.TryParse(counter.text, out Ecount);
        crc = crc + Poffset;
        crc = crc + Moffset;
        crc = crc + Toffset;
        crc = crc + Ecount;
        System.Threading.Thread.Sleep(1000);
        sina.WriteLine("M" + crc.ToString());
        System.Threading.Thread.Sleep(1000);
        sina.WriteLine("E" + counter.text);
        plus.WriteLine(plusoffset.text); plus.Close();
        minus.WriteLine(minusoffset.text); minus.Close();
        lenght.WriteLine(lenghtoffset.text); lenght.Close();
        */
    }
    public void plusinc()
    {
        int value;
        int.TryParse(plusoffset.text, out value);
        value++;
        plusoffset.text = value.ToString();
    }
    public void plusdec()
    {
        int value;
        int.TryParse(plusoffset.text, out value);
        value--;
        plusoffset.text = value.ToString();
    }
    public void minusinc()
    {
        int value;
        int.TryParse(minusoffset.text, out value);
        value++;
        minusoffset.text = value.ToString();
    }
    public void minusdec()
    {
        int value;
        int.TryParse(minusoffset.text, out value);
        value--;
        minusoffset.text = value.ToString();
    }
    public void lenghtinc()
    {
        int value;
        int.TryParse(lenghtoffset.text, out value);
        value++;
        lenghtoffset.text = value.ToString();
    }
    public void lenghtdec()
    {
        int value;
        int.TryParse(lenghtoffset.text, out value);
        value--;
        lenghtoffset.text = value.ToString();
    }
    public void load_offest()
    {
        System.Threading.Thread.Sleep(500);
        System.IO.StreamReader offset = new System.IO.StreamReader("c:\\offset.txt");
        string stroffset;
        stroffset = offset.ReadLine();
        plusoffset.text = stroffset;
        stroffset = offset.ReadLine();
        minusoffset.text = stroffset;
        stroffset = offset.ReadLine();
        lenghtoffset.text = stroffset;
    }
    public void clear()
    {
        sendgcode.text = "";
        plusoffset.text = "";
        minusoffset.text = "";
        lenghtoffset.text = "";
    }
    void OnSerialLine(string line)
    {
        Debug.Log("Got a line: " + line);
    }
}*```

Answer 1

In your do - while loop you constantly keep writing the string str1 . This looks already quite odd.

And then you do board = sina.ReadExisting() which returns all currently available stream and buffer content.

Reads all immediately available bytes, based on the encoding, in both the stream and the input buffer of the SerialPort object.

Since this is a stream and there is no sich concept as "messages" might be multiple lines/messages or also only a part of one => pretty unlikely that this matches exactly with what you have sent immediately.

You would need to come up with a proper protocol like eg using a special separator character between messages.

Rather use ReadLine which reads until the next encounter of the configured NewLine character (by default \n ) or use ReadTo(string) for a string pattern.

Both will "freeze" until according character is received making sure the entire message is fully received before continuing in your code.

So instead of

do
{
    sina.WriteLine(str1);
    board = sina.ReadExisting();
    Debug.Log(board);               
}
while (board != str1);
sina.WriteLine("$");

you would probably rather do something like eg

sina.WriteLine(str1);
do
{
    board = sina.ReadLine();
    Debug.Log(board);               
}
while (board != str1);
sina.WriteLine("$");

IF a loop is what you want to use at all.

---

In general I would always use two separate threads for sending and receiving. Except you have a clear protocol where you only need to be able to receive in certain slots in the logic.