RS-232 异常行为

Question

Windows 10-64. I coded a small VB application last fall, to drive a "PR-705" serial device from the RS-232 port. It worked flawlessly. Now, whenever I fire that code, the PR-705 is not responding so nicely? I originally used a FTDI-based USB to RS232 adapter (Thunderlinx 1000) which worked perfect. I figured, the problem might have to do with the "driver"? So I added a PCI-Express serial port card from StarTech to my PC. The result: no improvement - same erratic behavior? Out of curiosity, this morning, I fired my trusty Windows HyperTerminal and it worked flawlessly (out of the PCI-e port)! So I know the trouble does not come from the device itself (sigh!) but somewhere in the chain of communications.

The problem I run into is as follows (hopefully, you can detect a "pattern"):

a) Open the serial port b) Send a command to the port, in an ASCII string (eg "M1") <- Device responds by sending data back In order to obtain ALL data from device, however, I have to send additional commands: c) "D2" d) "D3" e) "D4" f) "D5"

When I run these commands from HyperTerminal, I get stellar behavior.

In my application, however, the additional commands ("D2", "D3", "D4" and "D5") are not getting THROUGH to the device, somehow? When I send "D2", for example, I get "XYZ" data back, which is OK. But when I follow-up with "D3", I still get the same "XYZ" data back? It is as though the new command ("D3") never reached the device?

My (ugly) workaround is to resend the same command over and THEN I get the new data (most of the time).

Here is some of my code:

Dim myPort As New IO.Ports.SerialPort("COM2") With {
            .BaudRate = 9600,
            .DataBits = 8,
            .StopBits = IO.Ports.StopBits.One,
            .Parity = IO.Ports.Parity.None,
            .Handshake = IO.Ports.Handshake.RequestToSend,
            .RtsEnable = True,
            .DtrEnable = True,
            .ReadTimeout = 1000000,
            .WriteTimeout = 10000
            }


myPort.Open()
myPort.WriteLine("M1")
myPort.WriteLine("D2")
Incoming = myPort.ReadLine() 

myPort.WriteLine("D2")
Incoming = myPort.ReadLine()

myPort.WriteLine("D3")
Incoming = myPort.ReadLine() 

myPort.WriteLine("D4")
Incoming = myPort.ReadLine() 

myPort.WriteLine("D5")
Incoming = myPort.ReadLine()

I know the TimeOut value is "extreme" but the device can take up to 15 minutes to reply, depending on the circumstances. I can't close the port before the device responds back otherwise I'll get an error, something to do with CTS, and then device automatically reboots -- not ideal. I'm not a RS-232 expert but I do the best I can with the little knowledge I have.

Answer 1

Found a partial answer to my serial port problem but this solution is not without its own problems. I found some c# code I adapted where the serial port "Received" is separated into its own "event". This works very well. As you'll see in the code below, it does the job. But now I'm facing the question of how to go about "successively" polling the port to get all the data returned by the instrument?

Here's the c# code first:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using System.IO.Ports;
using System.Threading;

namespace WindowsApplication14
{  
    public partial class Form1 : Form
    {
        string Operation, MesureM1, MesureD2, MesureD3, MesureD4;
        SerialPort _serialPort;

        // delegate is used to write to a UI control from a non-UI thread
        private delegate void SetTextDeleg(string text);

        public Form1()
        {
            InitializeComponent();
        }

        private void btnStart_Click(object sender, EventArgs e)
        {
            try
            {
                if (!_serialPort.IsOpen)
                    _serialPort.Open();

                _serialPort.Write("PR705\r\n");
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error opening serial port :: " + ex.Message, "Error!");
            }
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            _serialPort = new SerialPort("COM2", 9600, Parity.None, 8, StopBits.One);
            _serialPort.Handshake = Handshake.RequestToSend;
            _serialPort.RtsEnable = true;
            _serialPort.DtrEnable = true;
            _serialPort.DataReceived += new SerialDataReceivedEventHandler(sp_DataReceived);
            _serialPort.ReadTimeout = 500;
            _serialPort.WriteTimeout = 500;
            _serialPort.Open();

            _serialPort.Write("PR705\r\n");

        }

        private void btnM1_Click(object sender, EventArgs e)
        {
            Operation = "M1";
            _serialPort.Write("M1\r\n");    // 0000,111,3.896e+002,0.3371,0.3563
            Thread.Sleep(500);
        }

        private void btnD2_Click(object sender, EventArgs e)
        {
            Operation = "D2";
            _serialPort.Write("D2\r\n");   
            Thread.Sleep(500);
        }

        private void btnD3_Click(object sender, EventArgs e)
        {
            Operation = "D3";
            _serialPort.Write("D3\r\n");   
            Thread.Sleep(500);
        }

        private void btnD4_Click(object sender, EventArgs e)
        {
            Operation = "D4";
            _serialPort.Write("D4\r\n");
            Thread.Sleep(500);
        }

        void sp_DataReceived(object sender, SerialDataReceivedEventArgs e)
        {
            Thread.Sleep(500);
            string data = _serialPort.ReadLine();
            this.BeginInvoke(new SetTextDeleg(si_DataReceived), new object[] { data });
        }

        private void si_DataReceived(string data)
        {
            String Result = data.Trim();
            textBox1.Text = Result; 

            switch (Operation)
            {
                case "M1":
                    MesureM1= Result; // MesureBase = "0000,111,3.884e+002,0.3377,0.3570"
                    break;
                case "D2":
                    MesureD2 = Result;  // MesureD2 = "0000,111,3.674e+002,3.884e+002,3.322e+002"
                    break;
                case "D3":
                    MesureD3 = Result;  // MesureD3 = "0000,111,3.884e+002,0.2044,0.4862"
                    break;
                case "D4":
                    MesureD4 = Result;  //
                    break;
                default:                
                    break;
            }          
        }  
    }
}

In my main form, I have four buttons and a textbox. Button M1 is used to take a measurement (send "M1" command to the instrument). Buttons D2, D3 and D4 are used to retrieve data from the instrument.

In my old VB application, I used code like this, to successively retrieve data from the instrument:

myPort.WriteLine("M1")

myPort.WriteLine("D2")
Incoming = myPort.ReadLine()

myPort.WriteLine("D3")
Incoming = myPort.ReadLine()    

myPort.WriteLine("D4")
Incoming = myPort.ReadLine()

That was but I don't know how to accomplish the same thing using the 'separate' approach in c#? I tried lumping the read operations in the same "event" sub as the M1 button, like this :

private void btnM1_Click(object sender, EventArgs e)
{
    Operation = "M1";
    _serialPort.Write("M1\r\n");    // 0000,111,3.896e+002,0.3371,0.3563
    Thread.Sleep(500);

    Operation = "D2";
    _serialPort.Write("D2\r\n");
    Thread.Sleep(500);

    Operation = "D3";
    _serialPort.Write("D3\r\n");
    Thread.Sleep(500);

    Operation = "D4";
    _serialPort.Write("D4\r\n");
    Thread.Sleep(500);
}

But it does not work, I only get the "last" serial port "Read", the D4. The code never goes through D2 and D3.

How would you suggest I go about this? I have not shown you D5 yet… The D5 operation is the most involved as I have to do "two reads", one for one piece of data and then 201 successive reads, to retrieve wavelength data, like this :

myPort.WriteLine("D5")
Incoming = myPort.ReadLine() 

Temp = Split(Incoming, ",")
PeakWL = Convert.ToDouble(Temp(2))

For i = 1 To 201
   Incoming = myPort.ReadLine()  
   Temp = Split(Incoming, ",")
   nmValue(i) = CDbl(Temp(0))
   SpectralValue(i) = CDbl(Temp(1))
Next

I'm going to try to solve my problem myself but I would appreciate suggestions.