How do PC Whiteboards communicate with the PC?
PC Whiteboards use a standard RS-232 serial cable to communicate with the PC. The whiteboard controller generates up to 192 touch points per second, which are transmitted at 9600 baud to the PC. On the PC side, a driver runs under Windows and checks the designated serial port 200 times per second for incoming data. If data is available, the PC Whiteboards Dynamic Link Libraries (DLL) validates the data, saves it to a file, and updates the application screen. In Windows 3.1x and 95, PC Whiteboards do not use an Interrupt Request (IRQ) or require that one be available for the designated serial port. However, PC Whiteboards cannot access the port if another driver has opened the port and/or taken an IRQ resource for that port. With Windows NT, an available IRQ resource is required.
