ACR122u help in reading the card

Question

Private Sub Read(sender As Object, e As EventArgs) Handles MyBase.Load    

    Dim ReaderCount As Integer
    Dim ReaderCount As Integer
    Dim ctr As Integer
    Dim sReaderList As String
    Dim ctr As Integer
    Dim sReaderList As String


    For ctr = 0 To 255
    sReaderList = sReaderList + vbNullChar

    Next

    ReaderCount = 255

    ' 1. Establish context and obtain hContext handle
    retCode = ModWinsCard.SCardEstablishContext(ModWinsCard.SCARD_SCOPE_USER, 0, 0, hContext)


    ' 2. List PC/SC card readers installed in the system
    retCode = ModWinsCard.SCardListReaders(hContext, "", sReaderList, ReaderCount)



    ' Load Available Readers
    Call LoadListToControl(cbReader, sReaderList)
    cbReader.SelectedIndex = 0

    If connActive Then
        retCode = ModWinsCard.SCardDisconnect(hCard, ModWinsCard.SCARD_UNPOWER_CARD)
    End If

    ' Shared Connection
    retCode = ModWinsCard.SCardConnect(hContext, cbReader.SelectedItem.ToString(), ModWinsCard.SCARD_SHARE_SHARED, ModWinsCard.SCARD_PROTOCOL_T0 Or ModWinsCard.SCARD_PROTOCOL_T1, hCard, Protocol)

    connActive = True


    Connect()

End Sub

Public Sub Connect()

    Dim tmpStr As String
    Dim indx As Integer


    validATS = False
    Call ClearBuffers()
    SendBuff(0) = &HFF                              ' CLA
    SendBuff(1) = &HCA                              ' INS


    SendBuff(3) = &H0                               ' P2
    SendBuff(4) = &H0                               ' Le : Full Length

    SendLen = SendBuff(4) + 5
    RecvLen = &HFF

    retCode = SendAPDUandDisplay(3)

    If retCode <> ModWinsCard.SCARD_S_SUCCESS Then

        Exit Sub

    End If


    For indx = 0 To (RecvLen - 3)

        tmpStr = tmpStr + Microsoft.VisualBasic.Right("00" & Hex(RecvBuff(indx)), 2) + " "

    Next indx

    cardUID = tmpStr

    Attendace_Menu.Show()
    Me.Hide()

End Sub

I need help with my code. I want it to read the UID of the smart card not just when loading the form but also when I remove the card and insert it again. It only reads the card when I load the form. I have no idea what to do since I'm new to programming and this is my project for school.

Answer 1

You can use WinSCard library's SCardGetStatusChange function to observe changes via background worker thread.