Using MSComm Input property

[wallacej]

Hi
I currently have a MSComm control (piezoComm1) which I use to send commands to a device attached to COM1.
I am using the Output property to send commands to the device, eg. MOV A25 which will move the device to 25 microns. This is working fine as I have tested the device's position using Hyper Terminal. However, I would like to test the position of the device within my VB project and display the results in a label on the form. Heres my code:

Private Sub cmdGo_Click()
    frmMain.piezoComm1.Settings = "115200, N, 8, 1"     'set baud rate, parity, data bits and stop bits
    frmMain.piezoComm1.CommPort = 1                     'set PC COMM port
    frmMain.piezoComm1.InputLen = 0                     'retrieve all of the input buffer
    frmMain.piezoComm1.InputMode = comInputModeText     'input buffer to receive text - not binary
    frmMain.piezoComm1.PortOpen = True                  'open port
    frmMain.piezoComm1.Handshaking = comRTS             'request to send handshaking
        
    frmMain.piezoComm1.Output = frmMain.Text1 + Chr$(13) + Chr$(10) 'send command in text box
    frmMain.lblResult1.Caption = frmMain.piezoComm1.Input           'put contents of input buffer into label
 
    frmMain.piezoComm1.PortOpen = False                 'close port
End Sub

When I type the query position command "POS? A" in the text box and click the button the designated label disappears, as if its caption value is set to blank/nothing. I am confident that this command works as I have used it in Hyper Terminal.

Can anybody shed some light on this problem?

Thank you in advance

Wallace

[foae]

You shouldn't put line:" frmMain.lblResult1.Caption = frmMain.piezoComm1.Input " into cmdGo_Click(). I suggest U to use the OnComm event and fire this command there. I would work better.

[zaza]

To clarify foae's post, you are sending info to the serial port and then immediately attempting to read back in from it. The port will not respond in such a time, and hence you simply don't get a respone. A better approach would be to finish executing the command and then listen to the port, monitoring what comes in and waiting until you get what you expect. Certainly you will have to wait longer than the time it takes for the code to execute from one line to the next.

zaza

[foae]

yeah, zaza is right. In fact, sometimes i use a small delay time (about 50ms) oin the 1st line of OnComm event by using sleep API. But you can also use just some command lines => that's enough