区分大小写的MSComm字符串

Question

I some experience coding, but none with VBA (Excel 2013). I am attempting to write an extremely simple program which, through the serial port, 1.) Tells a remote device to accept external commands ("PHOTO"), 2.) Sends an external command ("M5" & Chr$(13)), and 3.) Tells the device to no longer accept external commands ("q").

Private Sub CommandButton1_Click()

    ' Use COM2
    MSComm21.CommPort = 2

    ' 9600 baud, no parity, 8 data, and 1 stop bit.
    MSComm21.Settings = "9600,N,8,1"

    ' Open the port.
    MSComm21.PortOpen = True

    MSComm21.Output = "PHOTO" ' Step 1
    MSComm21.Output = "M5" & Chr$(13) ' Step 2

    ' Do some stuff


    MSComm21.Output = "Q" ' Step 3

    ' Close the port
    MSComm21.PortOpen = False

 End Sub

My problem is that, while I can confirm that steps #2 and #3 work, step #1 does not. When talking to the device in Tera Term, the "PHOTO" command must be sent in all caps, while the "M5" and "q" commands are not case sensitive. I'm wondering if the MSComm21.Output command disregards case? I haven't been able to find anything specifically talking about this. If not, is there something obvious that I am missing?

This "simple" program is driving me insane, any help at all is appreciated.

Answer 1

I switched the line:

MSComm21.Output = "PHOTO" ' Step 1

with:

MSComm21.Output = "P"
MSComm21.Output = "H"
MSComm21.Output = "O"
MSComm21.Output = "T"
MSComm21.Output = "O"

And I was able to get it to work. Thanks.