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[on:]

...I see a lot of references to the 'SOMO 14D' sound replay module, but I thought ~$25 for a module
with the specs it has was just a wee bit too expensive. The modules is made be 4Dsystem in my
own locale (.au), and the forums on that site suggest the module's main IC has all it's identification
sanded off, and thus nobody knows what it is... well... I think I do...

...searching around for a comparable module, I came across the following ;

 http://emartee.com/product/41540/MP3%20Sound%20Module%20Mini%20SD%20Card

..albeit the PCB design is different, pinouts are not the same, and you have to ensure you order the
right control mode preprogrammed into it... but otherwise, it's functionally identical to the SOMO 14D,
<half the price, and likely they're both using the same (or very similar) IC -- the WTV020-s(SOP20) ..
.. so you can grab the documentation from the above page and use them for reference...

...this also means that much of what applies to the SOMO 14D applies to the 'WTV-020-SD-mini'
(as marked on the PCB) from emartee.com -- that means you can use the 'SOMO Tool' from the
4Dsystems website (it's a free download) to produce the 4bit ADPCM '.ad4' compressed audio files
used by these modules, and sketch examples all work 'as expected' for both...

  http://yapan.googlecode.com/svn/trunk/arduino/examples/SOMO_14D_Test/SOMO_14D_Test.pde

...be mindful that this IC was primarily designed to deliver audio content at or about the sound
frequency of the human voice, and as such the dynamic range of the audio output is limited. And
it's mono only. If you want a talking project that has a 'vocabulary' of up to 512 voice/sound samples,
that can babble on like any scifi teevee robot/computer/ship for about $10 ... this is you =) If you want
a something to replay *music* in stereo at a more acceptable fidelity for listening, don't use these modules,
you'll be disappointed -- buy something better....

[Reply #1 on:]

Oh, that's very good to know, thank you so much.  I was also wondering on that same chip (found on eBay) for music, but yeah, it sucks for music, its more "robotic" voice oriented. ;-)

Wk

[Reply #2 on:]

...yeah, I consider a baseline here to go something like this - if the datasheets do -not-
reference the audio signal quality (frequency response, S/N ratio, blabla) then it's a fair
bet you don't want to know =)  Not for music anyhow ... but for voice/sound effects
these things work great...

....what I did forget to include here yesterday, was the 'end of the paper trial' ... these
IC's with a nomenclature starting with 'WT' are all made by this company, 'waytronic' ;

 http://www.waytronic.com/product_show.asp?pid=114

...and there you can cite the various versions, and the sound module I speak of here (they
probably OEM them to emartee and others) - it gave me the reference to the SOMO 14D
as using the WTV-020. What I did find really interesting though, was this construct ;

 http://www.waytronic.com/product_show.asp?pid=155

...within the niche usage area it's intended for, man could you have some fun with that .. =)

...anyhow, the same company makes other IC's of this type, and it looks like there's a meaning
wrt the 'V' in the part number -- they also make 'M' versions, which at a guess equates to
'music'  instead of 'voice'. Functionally, they're almost the same as the WTV variant but with
a few extra tricks.... ;

  http://www.waytronic.com/product_show.asp?pid=93

...which you can find on emartee as well...;

  http://emartee.com/product/41932/Mini%20MP3%20SD%20Card%20Sound%20Module

... I also have one of these, I haven't had time to connect it up yet, but, my guess is this module
is more adept at music replay. It's around 4 times the footprint of a WTV-020-SD-mini, and they've
lovingly sanded off the IC markings to obscure the truth .. (well, almost - 1 IC is bound to be the
WTM chip, and the other IC is some Atmel chip... the sander didn't quite remove the logo and
both chips are fed a 16mhz xtal clock ; seems difficult to find specs on the WTM chips, but, with
these the english mentions 'music' and 'mp3 audio replay' and that possible uses include MP3 players,
and the word 'voice' is noticeably absent. When I get to it, I'll post a thread here in that regard...

Cheers!

 

[Reply #3 on:]

...back to the WTV-020-SD-mini ... as mentioned above, I was curious as
to what the audio output was actually doing in real life, so last night I
hooked the freq.generator & 'scope up to it and had a realtime look...

.... it's kinda like a midrange bandpass that rolls on @ ~1khz and rolls off
steeply beyond 10khz ..it's peak notch is about 3.5khz, and not surprisingly
this is pretty much perfect for 'voice'. When you consider the other components
here...ie; the DAC capability, limited sampling rate of samples (and the actual
4bit compression artifacts if you're using .ad4 format) etc, the module is 'sanely'
spec'd so to say =)

...for clarity (or fun =), I should have mentioned you can monitor the state of
pin15 of these modules (iirc the same is so for pin5 of the somo-14d), to determine
when a sample has finished playing. This pin goes HIGH while replay is in progress,
and goes LOW again when the current replay is finished. The what I want to do
with this module is recreate the robotic voicing effect used in Syndrome's flying
submersible airplane in 'The Incredibles' ... I've always liked that computer voicing,
the utter lack of proper intonation in the concatenated sentences of words ; using
the state of this output pin, will be a means to such ends...   

[Reply #4 on:]

Were you able to make it work with an arduino board? Have been trying for two nights and nothing.