Received waveform frequency is way too low than it was sent
My usual guess when I see frequencies that are way too low (orders of magnitude such as this example) is aliasing.  In order to see your 50 Hz waveform, you need to be sampling at a minimum of 100 Hz (and generally higher).  However, if you sample at something lower, specifically lower than 50 Hz, you will get an image frequency.  For example, if you sample the 50 Hz waveform at 0.6 Hz, you would get an image at 0.2 Hz (50-N*0.6) where N happens to be 83 for the frequency you'll actually see.