Trouble with active HPF (high pass filter)

[fezder]

hmm, thing is with that FFT library (seems i gotta use that, can't make any sensible bandpass filter.....)i really don't understand it, i mean i checked with 'scope that arduino sends bunch of data, but that data is useless without knowing how to pick those relevant pieces there

 

[jjw]

FFT-library has different functions how to handle output data.
Basically the data is available in some output array depending on the used function, for example fft_lin_out8[] is 8bit linear, fft_log_out[] is logarithmic scale ( desibels )
You could read the data in the array one by one and put it on a output port.

The example program in the library sends the data to serial output.