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Serial Port Drama

Posted on 2010-09-08
10
Medium Priority
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504 Views
Last Modified: 2013-12-17
Hi,

I am trying to do some simple comms via C# and a serial port however all is not quite working
as I expect.

I am trying to talk to my inbuilt modem and do a ATI4 <return> and I should get
back "HDA CX11270 Soft Modem" instead I get back the string I have
just sent.

I have included the code below.

Any ideas,

Thanks,

Ward.


using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO.Ports;

namespace SerialTest1
{
    class Program
    {
        static void Main(string[] args)
        {

            SerialPort sp = new SerialPort();
            sp.BaudRate = 9600;
            sp.PortName = "COM3";
            sp.DataBits = 8;
            sp.StopBits = StopBits.One;
            sp.Parity = Parity.None;
            sp.Open();
            sp.WriteLine("ATI4\r");
            string received_data = sp.ReadLine();
            sp.Close();

            // I should get back:  HDA CX11270 Soft Modem
            // but instead I get back ATI4

            Console.WriteLine("Data: {0}", received_data);
        }
    }
}

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Question by:whorsfall
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10 Comments
 
LVL 10

Expert Comment

by:effx
ID: 33625853
Have you tride the same command using Hyper Terminal?
0
 

Author Comment

by:whorsfall
ID: 33625880
well i am using different terminal software but it does work.
0
 
LVL 10

Expert Comment

by:effx
ID: 33625934
Try:

string received_data = Console.ReadLine();

instead of:

string received_data = sp.ReadLine();

0
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LVL 10

Expert Comment

by:effx
ID: 33625995
Scrub my last try:

sp.WriteLine("ATI4\r\n");

Instead of:

sp.WriteLine("ATI4\r");
0
 

Author Comment

by:whorsfall
ID: 33626062
Hi,

Thanks for your response same result

Ward
0
 
LVL 3

Expert Comment

by:aledev
ID: 33626654
Try to put this line

sp.WriteLine("ATE0\r");

before this one

sp.WriteLine("ATI4\r");

and see what happens
0
 
LVL 3

Accepted Solution

by:
vusov earned 1000 total points
ID: 33636281
Try to convert "ATI4" string to byte array and use sp.Write method
0
 
LVL 3

Expert Comment

by:aledev
ID: 33636501
If the echo of your modem is enabled, i think is normal that you read "ATI4" instead of  "HDA CX11270 Soft Modem" because the modem sends you back what you write (in this case "ATI4\r") so when you use ReadLine method it retrieves the first line in the buffer and probably the next one could be what you are looking for
Use this command for disable the echo and try again:

ATE0
0
 

Author Comment

by:whorsfall
ID: 33655650
Hi,

Ok I have made some changes and got it more succesfully working, maybee I could get an explination.

Here is the output.


Data:
HDA CX11270 Soft Modem
OK
 Length: 30


Code:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.IO.Ports;

namespace SerialTest1
{
    class Program
    {
        static void Main(string[] args)
        {

            SerialPort sp = new SerialPort();
            sp.BaudRate = 9600;
            sp.PortName = "COM3";
            sp.DataBits = 8;
            sp.StopBits = StopBits.One;
            sp.Parity = Parity.None;
            sp.Open();
            sp.WriteLine("ATI4\r");

            int bytes = sp.BytesToRead;
            string received_data = sp.ReadExisting();
            int length = received_data.Length;
            sp.Close();

            // I should get back:  HDA CX11270 Soft Modem
            // but instead I get back ATI4

            Console.WriteLine("Data: {0} Length: {1}", received_data,length);

            //Console.ReadKey();
        }
    }
}

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0
 
LVL 3

Assisted Solution

by:aledev
aledev earned 1000 total points
ID: 33656358
when use ReadLine method look at the NewLine property and be sure that it is set to "\r" instead of "\n"
0

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