I wrote a Win32 program several years ago to control an external device via the parallel port. It worked fine up through Windows 98, but ceased functioning once the port got tied up via the operating system. I still use the program on an old machine with Win98, but have been trying to explore future options. I could rewrite it to use parallel port drivers for later OSs, but the newer laptops don't have parallel ports anyway.
I really only want an On/Off signal and have even thought of just using the modem jack, or one of the serial control lines, but some of the laptops don't have these either.
So, I'm left looking at the one port they all seem to have in common - USB. I really don't want to have to build a circuit that handshakes with the port in order to work with it, but can't find anything that looks like it would simply set a state as in the old days.
Can anyone point me toward an API or some code that could simply cause a signal on one of the USB contacts? I would prefer a solid signal, but even a strobe could be useful if I could change whether it exists.
Thanks for any suggestions that may arise.