Hi Tim -
I've been working a lot with audio on the gumstix boards lately with varying
amounts of success. I have used three different board combinations:
1.) Overo + Summit -- In this combination the audio quality is terrible. I
don't recommend using the summit board for any kind of significant audio
2.) Verdex + GPSstix -- Fantastic audio quality. Measured -90dB noise floor
with 0dB of onboard gain. The only prevelent noise seems to be from the RTC.
3.) Verdex + Audiostix II -- Same as GPSstix.
I use line-in to record. Increasing the gain also increases the noise, but
the noise floor is still around -70dB.
I don't have any experience with audio output on the board, since I am
remotely recording files to view later. Are you sure most of your sound
quality issues aren't from the output hardware?
On Tue, Mar 3, 2009 at 1:12 PM, Tim Redfern <gumstix@...:
> I've been experimenting with the gumstix audio input with rather mixed
> I have audiostix II and gpsstix cards on connex & verdex boards. (rev 1171
> With a microphone input I'm getting a colossal buzzing sound. Definately
> not useable in any way.
> If I use a line level input and use aumix to tweak the mic input gain,
> output level, and the level
> of the signal going in, its better but it still seems to suffer from
> 'processor noise'.
> I have read this suggestion from Arlen Raasch:
> which seems quite difficult: unsoldering the smt resistor between the audio
> jacks and connecting
> 3 components in its place, also to a pin on the ucb-1400 chip? (if I've
> understood it)
> Can anyone confirm whether this should be necessary, if I can expect an
> Or has anyone had success with the audio on the Overo? Does it seem more
> electrically insulated
> from the rest of the computer than the audiostix?
> I listen to the audio on the iphone and it seems perfect even though it is
> so near to antennae,
> arm processor, rf transmitters.. I wonder how they manage this?
> > Hi List,
> > I'm working on a PCB for the Overo which will have a built-in microphone.
> > Do I need to pre-amplify signals from an electret microphone (such as
> > one
> > or is that taken care of by the TPS65950?
> > On the Summit schematic, I see the signals feed directly from the audio
> > connector to the LINE_IN_LA and LINE_IN_RA pins on the 70-pin connectors.
> > As the Overo schematics aren't available, am I safe to assume that the
> > bias circuitry described in the datasheet is on the Overo itself?
> > Also, as a side, I'm curious if there are any reasons why I shouldn't be
> > able to connect a single cell LiPoly battery directly to the Overo to
> > power. The Summit board says explicitly "5.0V ONLY" on the silkscreen,
> > I see no reason why when examining the schematics and TPS65950. Will
> > work OK?
> > Thanks in advance!
> > Brad
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