On May 2, 6:11 am, larlin <larlin...@gmail.com> wrote:
> I'm trying to sample low frequency signals on the headset microphone
> AD.
> The wolfson driver defines the 3 different filter options available on
> the chip, eg:
> static const char *adc_hpf_text[] = {"Hi-Fi","Voice 1","Voice 2",
> "Voice 3",};
I hadn't realized here was a software component to this. My gut
assumption would be that there's dc blocking (ie series) capacitor in
the input circuit.
I wouldn't be surprised if there is one even if there's also software/
DSP filtering involved.
If you want performance all the way down to 0 Hz you may need to look
at using a mixer circuit to modulate your low frequency input with say
a 12 KHz (assuming 48 Ksps) carrier frequency, and then demodulate it
in software. Ie, you use the input signal to control the amplitude or
frequency of a ~12 Khz oscillator, and then measure that
characteristic in software to recover the input signal.
--
unsubscribe: android-porting+unsubscr...@googlegroups.com
website: http://groups.google.com/group/android-porting
