Refer to UART signal on Arduino

Hello Everyone,

I have one question refer to UART signal on Arduino.

Now I am trying to use Arduino as just USB-UART converter.
Serial command is sent to external device from Agilent VISA via Arduino.

I made following code on VBA with Agilent VISA and send "1" as test.
Monitoring Arduino Pin0 (RX) and Pin1 (TX) like as attached but signal is appearing on Pin0 (RX).
( I guess signal might appear on Pin1 (TX) )

I am wondering this phenomena is correct or not.
If it's strange, is there any way to improve it ?

Sorry for your time but could you help to give me some advise.

'''''''''''''''''''''' VBA code with Agilent VISA '''''''''''''''''''''''''''''''''

Private Declare PtrSafe Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long) 'declare to use "sleep"
Dim RM As New VisaComLib.ResourceManager
Dim CD As New VisaComLib.FormattedIO488 'Arduino UNO
Dim IA As VisaComLib.ISerial

Private Sub CommandButton1_Click()

Set CD.IO = RM.Open("ASRL39::INSTR") 'Opening port
CD.IO.TerminationCharacterEnabled = False 'EOT dis-abled
Set IA = CD.IO
Sleep (100)
IA.Flush IO_IN_BUF 'clear buffer

Dim intSend(0) As Byte
intSend(0) = &H31

Dim ans As Integer
ans = CD.IO.Write(intSend, 1) 'send 1 byte

End Sub

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

Arduino_UART.PNG800×480 15.7 KB

Monitoring Arduino Pin0 (RX) and Pin1 (TX) like as attached but signal is appearing on Pin0 (RX).
( I guess signal might appear on Pin1 (TX) )

The labels are chosen from an Arduino point of view and not from a PC (USB) view. The signal sent by the PC is received by the Arduino, so it's available on the RX pin. The PC will receive data sent to the TX pin as that's what an Arduino usually is doing for debugging.

I am wondering this phenomena is correct or not.

It is correct and intended.

Hi pylon,

thank you for your prompt and kind reply.
I totally understand.

I am trying to connect target device tomorrow with this environment.

thank you.