Cts

Hi
how can i set THE CTS bit in an serial communications in Framework 1.1?

Hello there ; According to my knowledge ,
Carrier Detect (CD; pin 1) ,
Data Set Ready (DSR ; pin 6),
Ring Indicator (RI ; pin 9) and
Clear To Send (CTS ; pin 8)

are all inputs to your Computer , From e.g. the Modem.

In other words , CTS is a singnal From e.g. the Modem , and to you ,and is a signal that you may now send data.

So you cannot set CTS. But you can set Request to Send (RTS)

I downloaded the 101 samples from Microsoft DownLoadCenter ( Just search for 101 samples on Google) , and found a sample there on how to program the COM - port. I never managed to receive anything ,until I did the corrections suggested by Darwen. However ,the reading of the input lines mentioned above worked.

Here are the very few code-lines you need to read CTS etc ;

I have removed everything else but reading the signals above

Lets say you put all these codelines in a file ,like e.g rs232.cs and include it as a part of your project ,

PHP Code:

---

using System;
using System.Runtime.InteropServices;
using System.Text;
using System.Threading;

public class Rs232
{
   IntPtr hport= IntPtr.Zero;

#region "Enums";
   private enum Lines
   {
      SetRts = 3,
      ClearRts = 4,
      SetDtr = 5,
      ClearDtr = 6,
      ResetDev = 7,  // Reset device if possible
      SetBreak = 8,   //  set {the device break line.
      ClearBreak = 9 // Clear the device break line.;
   }
#endregion

#region "Win32API";
   [DllImport("kernel32", SetLastError=true)]
   static extern unsafe bool CloseHandle(IntPtr hObject);

   [DllImport("kernel32", SetLastError=true)] 
   static extern unsafe IntPtr CreateFile(string FileName,
                                               uint Access,
                                               uint Mode,
                                               uint Attrib,
                                               uint Disposition,
                                               uint Flags,
                                              int hTemplateFile);

   [DllImport("kernel32.dll")] 
   public static extern bool GetCommModemStatus(IntPtr hFile, ref int Status) ;
    
   [DllImport("kernel32.dll")] 
  private static extern bool EscapeCommFunction(int hFile, long ifunc);
#endregion

#region "Methods";
    public void Close()
    {
        CloseHandle(hport);
    }
    public int GetBits()
    {
        int lpModemStatus = 0;
        GetCommModemStatus(hport, ref lpModemStatus);
        return(lpModemStatus);
    }

    public void SetRts()
    {
        EscapeCommFunction(hport, (long)Lines.SetRts);
    }
    public void ClearRts()
    {
        EscapeCommFunction(hport, (long)Lines.ClearRts);
    }
    public int Open()
    {
        const uint GENERIC_READ = 0x80000000;
        const uint OPEN_EXISTING = 3;

        hport = CreateFile("COM1",GENERIC_READ,0,0,OPEN_EXISTING,0,0);
        if (hport != IntPtr.Zero) return 1; else return 0;
    }
#endregion
} 


---

Now that you have rs232.cs as a part of your project ,you may use it in other parts of your code.

Lets say your main form is Form1.cs ,and you want to read the status lines there...from now on all happens in Form1.cs;

First put this in the beginning, were the rest of the stuff is declared;

PHP Code:

---

    private Rs232 m_CommPort = new Rs232(); 


---

Now the first thing you must do is to open the comport;

PHP Code:

---

   int result = m_CommPort.Open(); 


---

Now that the comport is open ,you may read the status lines as many times as you want ;

PHP Code:

---

   int Status = m_CommPort.GetBits(); 


---

Now the variable "status" will change as CD , CTS etc changes. ( this is bit oriented).

If you want to know whether CTS is high or low ,you must test the corresponding bit;

PHP Code:

---

int ClearToSend = true;      // These variables are just included for explanatory purposes
int DataSetReady = true;
int RingIndicator = true;
int SetCarrierDetect = true;


if( (Status & 0x10) >0)
   ClearToSend=true;
else
   ClearToSend=false;

if( (Status & 0x20) >0)
   DataSetReady=true;
else
   DataSetReady=false;

if( (Status & 0x40) >0)
   RingIndicator=true;
else
   RingIndicator=false;

if( (Status & 0x80) >0)
   CarrierDetect=true;
else
   CarrierDetect=false; 


---

I havent tested setting out to RTS ( But I've tested the input lines as shown above) , but it wouldnt suprise me much if the following line now in forms1.cs will set RTS "active" ;

PHP Code:

---

   m_CommPort.SetRts(); 


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As all readers probably know ,an active RS232 line is -12 Volts. A non-active line is +12 Volts.
This means that if you want to test CTS input active or not ,it wont do to connect it to ground. It must be connected to -12 Volt.

But most likely ,if you havent set RTS "non-active" , RTS will be -12 Volts. Therefore ,you can connect CTS to RTS ,in order to test CTS.