FSK Demodulation with ADAU 1701

Hello Lama,

You found the right post with two different ways to demodulate. So you want to mute the audio output when FSK is detected correct? 

Well, the first approach in the post you found is showing a way to do it. The output of the two filters are going through a peak envelop generator. That output can be summed and tested with a threshold level stored in a DC cell using an ABCD block like KJBob did. Then with that signal you invert it and use that to control a volume control. Most of the pieces are there. 

So what are you not able to get working? The FSK or the muting?

Feel free to attach your project. It usually saves time so we are not guessing. 

Dave T

Hello Dave,

here is my project:

Design_Demodulation.zip

I am still working on detection. I guess muting will be easy.

Made some progress, so now I can measure the GPIO 2 and 3 outputs on a logic analyzer. If I play a pure 1300 Hz sine wave tone, GPIO 2 becomes Low Level. On 2100 Hz it becomes high level. When I lower the Level for threshold to 0.02, I see GPIO 2 level too.

But I am a little bit disturbed by the fact that when I raise the input volume above 30 %, the audio output on the speaker has more and more gaps.

When I play a pure sine tone of 1300 Hz, I do only have these hickups - no real tone at all.

However, with my real FSK signal, I detect nothing at all.

The gaps come from insufficient Power supply. Sorry for this inconvenience

The gaps come from insufficient Power supply. Sorry for this inconvenience