>From a pin allocation prospectively, allocating the right McASP pins may
introduce other problems (pin sharing, etc). The ADCs have dedicated analog
pins to avoid this.
For basic ("telephony quality") audio, the ADCs are quite work able. Things
you need to consider are -
- Signal conditioning (converting the mV range into a signal that fits
0-1.8V). Biasing is pretty easy - a cap and a resistor should work with many
mics.
- Noise filtering.
- Software
- The reference on the BBB is hard wired to 1.8V.
I have gone down this path and have it working with PocketSphinx. Highlights
of the journey -
- Opamps or single transistor AMPs do work but there is a lot of tuning needed
keep a usable signal from the ADC. over a range of distances to the mic
without having to do a lot of shouting or dealing with clipping.
- Using a single chip AGC/mic preamp does make things a lot easier to tune.
- The ADC is quite noisy.
- The output sample rate is 8KHz. There are different settings that can give
you 8KHz on the ADC but they have different noise characteristic. The settings
will have to be tuned to match the signal conditioning circuit.
- Data output via a simple character driver. Original plan was to get this
into ALSA but haven't found time for that yet. IIO is nice but that requires
some kind of userland decoding for pocketsphinx. The character driver outputs
match the 'file' input format for pocketsphinx.
On Thursday, July 14, 2016 19:16:30 John Syne wrote:
> You would be better off using an audio codec for this purpose.
> Unfortunately, the Audio Cape doesn’t bring out the microphone circuitry,
> but you could use a audio preamp and connect to the audio cape audio input.
>
> Regards,
> John
>
> > On Jul 14, 2016, at 3:26 PM, keerthana.manivan...@gmail.com wrote:
> >
> >
> > Hi there,
> >
> > I'm looking to use an electret microphone with a beaglebone black for my
> > project. Can't I directly plug the mic into an analog pin and use the
> > data? Do I need a pre amplifier circuit kind of thing to use the mic with
> > a BBB?
> >
> >
> > On Tuesday, March 10, 2015 at 11:49:16 PM UTC-5, sns wrote:
> > Will USB headset with mic work for audio application that records sound
> > and playback on beaglebone with quality?Here is there is no need for
> > separate pre- amplifier or circuit that requires biasing mic voltage?
> >
> > On Thu, Feb 26, 2015 at 2:53 PM, Zainab S.V <sv.z...@gmail.com
> > <javascript:>> wrote: What about using microphone input from a headphone
> > for recording and using the headset for playback? Does it need any extra
> > circuitry?
> >
> > On Tue, Feb 24, 2015 at 8:22 PM, Fredrik Olofsson <red...@gmail.com
> > <javascript:>> wrote: all the usb soundcards i've tried so far can don't
> > need biasing. just solder an electret mic directly to a minijack and
> > connect it to the input of the usb soundcard. though note that sound
> > quality varies. some cards make a lot of noise (one logilink model even
> > was blinking a led when active and that interfered and could be heard in
> > the mic input signal.) terratec aureon dual usb is the best sounding card
> > i've found so far. though i don't own an audio cape so i can't compare.
> >
> > If i use usb audio interface instead of the cape, is there a need for
> > biasing ?
--
Hunyue Yau
http://www.hy-research.com/
--
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