Reading Serial Port to USB GPIO Board

Hi All, I am working on a small project where I am trying to convert a Raspberry Pi / Python program to vb.net using a USB board that has GPIO pins. (Numato Labs GPIO). I am using the code they have on their website as Serial communication is a pretty new thing to me. I am simply trying to interface a tester unit to this board that has a "green" and "red" LED and trying to determine the output for "Pin High" or "Pin Low". The tester is nothing more than a ground connection, so the LED will be Green if pass or Red if fail. I am using a timer to trigger each second so I can sort of "monitor" the pins as the test can happen at anytime. I see various numbers on the code output, but it seems a little confusing to me. Most of my confusion is in the (Private Sub btnAnalogRead_Click). Any bit of explanation on this would be great. Thanks

In the lines below, I cannot figure out what these numbers mean? 13 & 10 / 14, 1

Code:

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Str(Val(Mid(readData, 13, 10))))

MsgBox("GPIO Status = " + Mid(readData, 14, 1))

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Code:

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'License
'-------
'This code is published and shared by Numato Systems Pvt Ltd under GNU LGPL
'license with the hope that it may be useful. Read complete license at
'http://www.gnu.org/licenses/lgpl.html or write to Free Software Foundation,
'51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA

'Simplicity and understandability is the primary philosophy followed while
'writing this code. Sometimes at the expence of standard coding practices and
'best practices. It is your responsibility to independantly assess and implement
'coding practices that will satisfy safety and security necessary for your final
'application.

'This demo code demonstrates how to use GPIOs and demonstrates how to read
'analog channel.

Public Class frmMain

    Private Sub btnOpenPort_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnOpenPort.Click

        On Error Resume Next

        ' Open the serial port selected. This GPIO device presents itself to
        ' the operating system as a serial port. So using this device is
        ' as easy as interacting with as serial port

        SerialPort1.PortName = "COM" + txtPortNumber.Text
        SerialPort1.Open()

        If (Not SerialPort1.IsOpen) Then
            MsgBox("Could not open the specified port", MsgBoxStyle.Critical)
        Else
            MsgBox("Port opened successfuly", MsgBoxStyle.Information)
        End If
    End Sub

    Private Sub frmMain_FormClosing(ByVal sender As Object, ByVal e As System.Windows.Forms.FormClosingEventArgs) Handles Me.FormClosing
        ' Close the serial port before exiting
        If (SerialPort1.IsOpen) Then
            SerialPort1.Close()
        End If
    End Sub

    Private Sub btnSetStatus_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnSetStatus.Click
        Dim gpioIndex As Char

        If SerialPort1.IsOpen Then

            If Val(txtGpioNumber1.Text) < 32 Then

                'GPIO number 10 and beyond are referenced in the command by using alphabets
                'starting A. For example GPIO10 willbe A, GPIO11 will be B and so on. Please
                'note that this is not intended to be hexadecimal notation so the the alphabets
                'can(go) beyond F.
                If (Val(txtGpioNumber1.Text) < 10) Then
                    gpioIndex = Chr(48 + Val(txtGpioNumber1.Text))
                Else
                    gpioIndex = Chr(55 + Val(txtGpioNumber1.Text))
                End If

                'Send a command to output the selected logic state to the selected GPIO.
                'The commands that is used to accomplish this acton are "gpio set" and
                '"gpio clear". It is important to send a Carriage Return character
                '(ASCII value 13) to emulate the ENTER key. The command will be executed
                'only when the GPIO module detects Carriage Return character.
                If (Val(txtGpioStatus.Text) = 0) Then
                    SerialPort1.Write("gpio clear " + gpioIndex + Chr(13))
                ElseIf (Val(txtGpioStatus.Text) = 1) Then
                    SerialPort1.Write("gpio set " + gpioIndex + Chr(13))
                Else
                    MsgBox("GPIO Status must be 0 or 1", MsgBoxStyle.Critical)
                End If
            Else
                MsgBox("Enter a valid GPIO number", MsgBoxStyle.Critical)
            End If
        Else
            MsgBox("Open a port before sending commands", MsgBoxStyle.Critical)
        End If
    End Sub

    Private Sub btnGetStatus_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnGetStatus.Click
        Dim readData As String
        Dim gpioIndex As Char

        If SerialPort1.IsOpen Then
            'Discard any existing data from teh receive buffer. This is an important step
            SerialPort1.DiscardInBuffer()

            'Read the state of the selected GPIO. The command that is used to accomplish this
            'acton is "gpio read". It is important to send a Carriage Return character
            '(ASCII value 13) to emulate the ENTER key. The command will be executed only
            'when the GPIO module detects Carriage Return character.It is important to note
            'that the device echoes every single character sent to it and so when you read
            'the response, the data that is read will include the command itself, a carriage
            'return, the response which you are interested in, a '>' character and another
            'carriage return. You will need to extract the response from this bunch of data.
            If Val(txtGpioNumber2.Text) < 32 Then

                'GPIO number 10 and beyond are referenced in the command by using alphabets
                'starting A. For example GPIO10 willbe A, GPIO11 will be B and so on. Please
                'note that this is not intended to be hexadecimal notation so the the alphabets
                'can(go) beyond F.
                If (Val(txtGpioNumber2.Text) < 10) Then
                    gpioIndex = Chr(48 + Val(txtGpioNumber2.Text))
                Else
                    gpioIndex = Chr(55 + Val(txtGpioNumber2.Text))
                End If

                SerialPort1.Write("gpio read " + gpioIndex + Chr(13))
                System.Threading.Thread.Sleep(10)
                readData = SerialPort1.ReadExisting
                MsgBox("GPIO Status = " + Mid(readData, 14, 1))
            Else
                MsgBox("Enter a valid GPIO number", MsgBoxStyle.Critical)
            End If
        Else
            MsgBox("Open a port before sending commands", MsgBoxStyle.Critical)
        End If
    End Sub


    Private Sub btnAnalogRead_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnAnalogRead.Click
        Dim readData As String

        If SerialPort1.IsOpen Then
            'Discard any existing data from the receive buffer. This is an important step
            SerialPort1.DiscardInBuffer()

            'Read the analog data from selected channel. The command that is used to accomplish
            'this acton is "adc read". It is important to send a Carriage Return character
            '(ASCII value 13) to emulate the ENTER key. The command will be executed only
            'when the GPIO module detects Carriage Return character.It is important to note
            'that the device echoes every single character sent to it and so when you read
            'the response, the data that is read will include the command itself, a carriage
            'return, the response which you are interested in, a '>' character and another
            'carriage return. You will need to extract the response from this bunch of data.
            If Val(txtAnalogChannel.Text) < 8 Then
                SerialPort1.Write("adc read " + txtAnalogChannel.Text + Chr(13))
                System.Threading.Thread.Sleep(10)
                readData = SerialPort1.ReadExisting
                MsgBox("Analog value = " + Str(Val(Mid(readData, 13, 10))))
            Else
                MsgBox("Enter a valid Analog Channel", MsgBoxStyle.Critical)
            End If
        Else
            MsgBox("Open a port before sending commands", MsgBoxStyle.Critical)
        End If
    End Sub
End Class

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Fully explained here:

https://docs.microsoft.com/en-us/dot...d?view=net-6.0