[LAU] [OT] Open Source Portable Recorder?

[Len Ovens]

On Mon, January 7, 2013 9:42 am, Johannes Kroll wrote:
> On Sun, 6 Jan 2013 08:48:35 -0800
> "Len Ovens" <len at ovenwerks.net> wrote:

>> As for hacking the unit itself, the first question is why. Not so much
>> why
>> you want to, but why would others want to. Before something gets the
>> firm/software hacked there generally needs to be a reason at least a few
>> people want to do so. Some extra functionality that is obvious (the
>> smart
>> phone has so much locked functionality it is frustrating so there are
>> lots
>> of hacks). The dr already seems to me to anything I would think of using
>> it for,
>
> As to why, I can think of a few things:
>
>  - triggering recording at fixed time intervals, or based on some audio
>    event like raised volume, or based on some external event, e. g. for
>    syncing to a video camera
>  - implementing USB audio so the device can be used as an external
>    microphone. The recorders I've seen only output an analog signal.
>  - changing recording parameters like custom sampling rates or different
>    encodings. Commercial ones mostly do uncompressed WAV or MP3, but no
>    lossless compression like FLAC for example.
>
> Other people probably have other ideas...

I was not trying to say it shouldn't be hacked, just that there needs to
be a large enough group of people who also see a need (or a why) for
hacking it before there is much support (so that you are not doing the
whole thing on your own). Those are all good reasons you have above (none
of which I had thought of) I am sure more would show up out of need too.

> Last not least, I simply like the idea of being in control of hardware
> I buy.

Nothing wrong with that.

> As to price: the DSO nano is a free/open source oscilloscope which
> isn't expensive at all, so building free and inexpensive hardware is
> possible. Actually, using the DSO nano as a base could be a good
> start for a recorder, it has A/D converters, mass storage and
> everything... Just no mics.

It could be a good base, but I think you may wish to add an A/d converter
with more than 4bit sample depth (at least it looks like to me) and single
channel. The sample rate is fine (though not fixed but variable so I don't
know how easy to set to 48k or whatever), but takes lots of CPU as the cpu
becomes part of the codec. However, there are lots of unused pins (i/o
ports) on the cpu and it is open so the possibility of adding something is
there. There is a schematic in the manual on
http://www.seeedstudio.com/depot/micro-digital-storage-oscilloscopedso-nano-p-512.html
for download which is where I got my info.

It has a display, buttons, battery, USB port, etc. I might be tempted to
add a second USB port (host instead of client) and use one of the cheap
USB audio ports (parts all in the USB plug) and some $5 mics. I just found
a great site for DIY mics That has some better pres than what comes with
the little electrets. (its on my other computer :P )


-- 
Len Ovens
www.OvenWerks.net