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Open Music Labs Forums • View topic - FHT to frequency
Page 1 of 1

FHT to frequency

PostPosted: Tue Jan 20, 2015 5:35 pm
by jbolfiil
Hello,

I am trying to get the FHT converted to frequency. I saw that the formula was k*(samples/FHT_N) but I can't seem to get what I want...

1. Does k need to be unsigned? I am getting negative values when ever I try to print it out to the serial monitor.

2. How do you find out what the sampling rate is? I have read that you need to look at the prescalar but I am not sure what that is.

I am just trying to write a high on a digital pin when a certain frequency is present. Any help will be appreciated!

Also, will I need to set a magnitude threshold somehow? I only want the high on the digital pin when there is an intentional sound.

(I just realized that I did not bias the signal so that maybe a cause for off numbers.)

Re: FHT to frequency

PostPosted: Tue Jan 20, 2015 9:14 pm
by guest
so to figure out which bin relates to what frequency, you need to know the sample rate. if you are using the default example from the library, that is 38kHz.

Frequency(k) = (k)*(sample_rate)/(FHT_N)

k is just the bin number.

if you want a pin to go high based on a certain frequency, just figure out which bin that is, and then check the value in that bin compared to a threshold, and set the pin high if its above the threshold

Re: FHT to frequency

PostPosted: Wed Jan 21, 2015 11:01 am
by jbolfiil

Re: FHT to frequency

PostPosted: Wed Jan 21, 2015 2:01 pm
by guest

Re: FHT to frequency

PostPosted: Wed Jan 21, 2015 8:40 pm
by jbolfiil

Re: FHT to frequency

PostPosted: Thu Jan 22, 2015 12:04 am
by guest

Re: FHT to frequency

PostPosted: Fri Jan 23, 2015 4:06 pm
by jbolfiil

Re: FHT to frequency

PostPosted: Fri Jan 23, 2015 4:17 pm
by guest

Re: FHT to frequency

PostPosted: Sat Jan 24, 2015 12:37 pm
by jbolfiil

Re: FHT to frequency

PostPosted: Sat Jan 24, 2015 9:42 pm
by guest