FSK demodulation using DSP

Hello all.Thanks for taking up your time to read my post.

Especifically talking, I need to demodulate a low frequency FSK signal( betwen 120 and 140 kHz ). I already have a circuit of antenna that receive the signal and I already can sample it, but I still have a doubt of how could be the best way, faster and reliable, to process the signal.

Basically, I'm using a comparator with interruption to count the number of cicles of the carrier, and a timer to measure the time between a pre-determined number of cicles. Depending on the time to count the pre-determined number of cicles it is decoded as being zero or one.

This is not working very well, it works, but it miss a lot too, so I was wondering an alternative way.

For those who may want to know, I'm using an AD734AN as the datasheet of http://www.kynix.com/uploadfiles/pdf/AD734AN.pdf.

Please, if some one has any Idea, I would appreciate very much!

Can anyone help me ? I am very puzzled about this question. I do need your help.

thanks in advance

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