GAMBAS BOOK 3.19.1

The SerialPort class (gb.net) was developed to enable communication via a serial interface (usually an RS-232 interface). This class inherits from the stream class, so you can use standard streams to send and receive data and close the port. You can create the class.

Dim hSerialPort As SerialPort
hSerialPort = New SerialPort() As "RS232" ' Event name

Table 24.1.5.0.1: Constants of the class SerialPort

The applicable constants from the Net class (gb.net) also apply. For example, the status property is set to Net.Active after successfully opening the serial port via SerialPort.Open().

The SerialPort class has these properties:

Table 24.1.5.0.2: Properties of the class SerialPort

The class has these seven methods:

Table 24.1.5.0.3: Methods of the class SerialPort

The SerialPort class has these events:

Table 24.1.5.0.4: Events of the class SerialPort

With this source code, a temperature value from a temperature sensor (DAC) is read out, interpolated and displayed every 500ms via a serial interface USB-RS232 adapter:

' Gambas class file
 
Public hRS232 As SerialPort
Public sTemperatureDigit As String
Public TTimer As Timer
 
Public Sub Form_Open()
 
  FMain.Center
  FMain.Resizable = False
 
  hRS232 = New SerialPort As "hRS232"
  TTimer = New Timer As "TTimer"
  TTimer.Delay = 500 ' The temperature is read out every 500ms
  SetLEDColor(pboxStatus, "red")
 
  StartMeasurement()
 
End
 
Public Sub StartMeasurement()
 
  hRS232.PortName = "/dev/ttyUSB0"
 
  hRS232.Speed = 4800
 
  hRS232.DataBits = SerialPort.Bits8
  hRS232.StopBits = SerialPort.Bits1
  hRS232.Parity = SerialPort.None
  hRS232.FlowControl = SerialPort.None
 
  Try hRS232.Open(3)
  If Error Then
     Message.Error(("Error when opening the V24-RS232-USB adapter interface!"))
     SetLEDColor(pboxStatus, "red")
  Else
     If hRS232.Status = Net.Active Then
        TTimer.Start()
        Print hRS232.DTR
        Print hRS232.DSR
        Print hRS232.Blocking
        Print hRS232.CTS
        Print hRS232.RTS
     Endif
  Endif
 
End
 
Public Sub hRS232_Read()
  Read #hRS232, sTemperatureDigit, Lof(hRS232)
End
 
Public Sub TTimer_Timer()
 
  If hRS232.Status <> Net.Active Or If Asc(sTemperatureDigit) = 0 Then
     lblTemperaturAnzeige.Text = "--- °C"
  Else
     lblTemperaturAnzeige.Text = Str(Interpolation(Asc(sTemperatureDigit))) & " °C"
     TextBox1.Text = Asc(sTemperatureDigit)
     pboxStatus.SetFocus()
     SetLEDColor(pboxStatus, "green")
  Endif
 
End
 
Private Function Interpolation(iArgument As Integer) As Float
 
  Dim fX0, fX1, fY0, fY1, f As Float
 
' Experimentally determined data points
  fX0 = 22
  fY0 = 22.3
  fX1 = 30
  fY1 = 34.5
 
' Interpolation
  f = ((fY1 - fY0) / (fX1 - fX0)) * (iArgument - fX0) + fY0
 
  Return Round(f, -1)
 
End
 
Private Sub SetLEDColor(picBox As PictureBox, sLEDColor As String)
  picBox.Picture = Picture["LED/led_" & sLEDColor & ".svg"]
End
 
Public Sub Form_Close()
 
  If hRS232.Status = Net.Active Then
     hRS232.Close()
     FMain.Close()
  Endif
 
End

Figure 24.1.5.0.1: Temperature display