Hardware: Shortest delay to send an ouput signal using windows

I would like to set an output from my computer high or low. This will change roughly 5 times a second. I will be measuring the output on an oscilloscope. The important thing is to make the time between requesting the change in software and the output changi开发者_如何学编程ng state as short as possible. The shorter the delay, the more accurate my result.

Does anyone know which of the following options has the shortest delay in a windows environment (it has to be in windows)?

1. USB
2. Serial
3. Parallel Port
4. Something else?

I could try all three and measure the difference, but presumably someone else has done this already?

Thanks!

Serial and Parallel will be lower latency that USB (I would expect) as the "height" of the stack between you and the port is smaller. Measuring the latency would be challenging - how will you know when the bit of code which writes to the port is executed?

However, even with a low potential latency, the jitter induced by windows is likely to be quite large as well.

Vaguely related and quite interesting... https://superuser.com/questions/419070/transatlantic-ping-faster-than-sending-a-pixel-to-the-screen/419167#419167

USB can transmit data the fastest by far.