Help With Dtmf

[Rivero]

:headbang: Some one could give me some tips to how decode dtmf?

thanks...

[Jim Kring]

I might be oversimplifying the problem, but...

A power spectrum of your signal should produce a spectrum with a single large peak. Find the frequency of the peak and you're done.

[Michael Aivaliotis]

Well, Jim is partialy right. You need to decode 2 frequencies. These are added to determine the X Y coordinates of the keypress. Three frequencies define the columns and 4 frequencies define the rows of the keypad. In any case, if you open the LabVIEW example called - Sim Phone.vi, you will see what I mean.

I have built a VI that decodes the DTMF tones of a common telephone. I tried it on my crappy handset at home using a microphone attached to my headset and it seemed to work fine. If this is for a test system, I recommend a high quality microphone. There seems to be alot of variation in frequency. You might have to tweek the frequency ranges I selected in the decoding section of the VI. If you don't want to use a real telephone then you can use the LV Sim Phone.vi example (i've included it in the attached llb) with your PC sound card.

The attached VI is LV7.0. You might need some advanced analysis DLL's that are only available in the LabVIEW full development version.

If anyone who downloads this code can improve upon it then please do so and upload it back to this topic so all can benefit.

Download File:post-10-1080893317.zip

[Rivero]

Thanks a lot Michael, that will be very useful for my final graduation project, i will put yor name in the credits.

[gobeirne]

Nice work Michael - cheers