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>>Dmitry, Did you know the commucication protocol and the COM settings device expected?
>
>Not yet. A prospective customer asked me if I could write an interface to communicate with a device connected to RS232 serial port. So far, this is all I know. I am trying to compile a list of questions I need to ask them and also understand conceptually what is involved in writing such interface using VFP 9.

It is easier.
Put MSCOMM32.OCX in a form. Make all its adjustments:
.Settings = "9600,n,8,1" && means Speed - 9600, parity - none, 8 data bits, 1 stop bit
.Port=1 && COM port 1 will be used
.RTSEnable = .f. && Request To Send line is not used
.Handshaking = 0 && Not used

and all others, read help for this.

Then

.PortOpen = 1 && This will open the port for comunicaton

The all that you must do is to sit and wait when something comes through port. If something comes that will occur in OnComm Event of the ActiveX control.
Here in download section there is a file that use that ActiveX, I'll try to earch it and will send you a link