Oscilloscope api for compact framework

Question

Few days ago I where searching for human interface for mobile devices. but all bluetooth devices are pretty messy and hard to implement.

Question are: "Is there open source, or free library for making Oscilloscope on WinMobile platform.
As my interface is not going to be human, I will try to make some kind of buzzer which is going to send sound commands to WinMobile device, at other side WinMoilbe device should be able to read frequency of buzzer tone and recognize command.

Moved to other question

So far my research telling me that there is no free library for voice recognize. Is this still a case, (because all post I found is old few years).

Answer 1

Being able to read the frequency is fairly simple. You need to use the waveInXxxx APIs to capture the incoming sound, then you can run an FFT on that data to determine frequency.

MSDN has an example of using the waveInXxxx functions from the CF. The SDF has two FFT algorithms.