I believe the data is in the buffer, but something else in your code prevents the OnComm from running under some circumstance. Are you doing anything with timers, Autoyield, or DOEVENTS anywhere else in this form?

>Hi,
>
>Thank for your advise. My RThreshold is set 1 for the OnComm event to trigger.
>InbufferSize = 1024.
>I tested using your code, there are no error detected in the OnComm events at all.
>In addition, I had even enable the Handshaking - Xon/Xoff.
>
>FYI, when I comment out the OnComm event code, had another button
>just to INPUT the buffer, the ETX is seem in the buffer.
>
>It seem like the MSCOMM didn't trigger the OnComm event for the ETX