David,
The weighing software receives a string of text data from the weighbridge via a RS232 port. It captures and then displays the current weight constantly. The software also generates weighbridge tickets confirming a vehicle's weight on its round trip in and out of the compound. (e.g when it comes in, if it is delivering goods, it will weigh more than when its on its way out. The system then prints out a ticket to confirm the entry and exit weight and the net weight to determine whether its a purchase or sale transaction)
Now, the customer wants to use the software to fill oil tankers. A picture of the tanker is to be displayed and a set point for the filling is keyed into the system. Once the filling starts, the software will show the percentage filled on the picture of the tanker. Once the target weight is achieved, the software is to send out a signal via an I/O card to trigger the closing of the valve.
I'm using MSCOMM32 for the reading of the RS232 data but not sure how to trigger the valve. More unsure what would happen if the PC somehow hangs!
Yau