通过USB GSM调制解调器发送短信

Question

I am trying to develop a module to send SMS from my application. The problem is that when I send an AT Command to a connected cell phone, my app stops responding. I'm using a Nokia 6720C and I have installed Pc Suite. It also appears in the Com Ports.

My code is below. What am I doing wrong?

Imports System
Imports System.IO.Ports
Imports System.Threading
Imports System.ComponentModel

Public Class Form1
Delegate Sub SetTextCallback(ByVal [text] As String)
Private Sub btnSend_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSend.Click

    With SerialPort1
        .PortName = "COM14"
        .DataBits = 8
        .Parity = IO.Ports.Parity.None
        .StopBits = StopBits.One
    End With

    SerialPort1.Open()
    SerialPort1.Write("AT" & vbCr)
    SerialPort1.Close()
End Sub

Private Sub SerialPort1_DataReceived(ByVal sender As Object, ByVal e As System.IO.Ports.SerialDataReceivedEventArgs) Handles SerialPort1.DataReceived
    ReceivedText(SerialPort1.ReadExisting())
End Sub

Private Sub ReceivedText(ByVal [text] As String)
    'compares the ID of the creating Thread to the ID of the calling Thread
    If Me.TxtResponse.InvokeRequired Then
        Dim x As New SetTextCallback(AddressOf ReceivedText)
        Me.Invoke(x, New Object() {(text)})
    Else
        Me.TxtResponse.Text &= [text]
    End If
End Sub

Answer 1

Well, at the end of the AT command you must add Chr(13) and Chr(10), you used Chr(13) only (which is "vbCr"), try replacing it with vbCrLf (Carriage-Return "Chr(13)" and Line Feed "Chr(10)"). I think this is the problem (the command string is not complete).

If the problem still resides, try the following to test your work:

1. Try using your VB.NET code to communicate with a GSM modem (not your phone). If it works fine, then maybe the phone does not accept AT commands.

2. Try using a terminal program to send the AT command to the phone. The terminal program can be like "Hyper Terminal" or "Maestro Smart Terminal" (you can search for it on google).

I hope this was helpful, good luck.