Hi @Lesiastas Here you have a simple VB UART loopback example, TX = RX = DIO-0 Dim hdwf As Long If FDwfDeviceOpen(-1, hdwf) = False Then Dim szError As String Call FDwfGetLastErrorMsg(szError) MsgBox("Device open failed" & vbCrLf & szError, vbExclamation + vbOKOnly) End End If Dim szTx = "Hello\n" Dim rgTx = System.Text.Encoding.ASCII.GetBytes(szTx) Dim rgRx(512) As Byte Dim fParity As Integer Dim cRx As Integer Call FDwfDigitalUartTxSet(hdwf, 0) Call