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Re: [Discuss-gnuradio] OLPC - next generation with SDR?

From: Robert McGwier
Subject: Re: [Discuss-gnuradio] OLPC - next generation with SDR?
Date: Tue, 25 Dec 2007 14:41:10 -0500
User-agent: Thunderbird (Windows/20071031)

Frank Brickle wrote:
> On Dec 24, 2007 5:11 PM, John Gilmore <address@hidden
> <mailto:address@hidden>> wrote:
>     The Odyssey board operates at 10MHz IF; so wouldn't it need an external
>     tuner?
> Yes, but many different tuners (band sets) can be serviced by the same
> IF processor.

Not to mention that Odyssey can take a few dollar DDS input in place of
the crystal and tune all of the HF shortwave bands.  The performance
will go DOWN because of the spurs generated by the inexpensive DDS but
that is probably acceptable as opposed to people not having a shortwave
radio at all or only those they cannot afford.   Further, to increase
performance, some kind of band switching apparatus, strictly for front
end filtering changes, needs to be provided.

>     What kind of antenna would this require?  Something external to the
>     laptop?  Or something that could be built into the plastic case?
> Depending on the band it could be either or both. A multiloop MW/HF
> could be embedded in the plastic case. A gender-bent SMA could
> accommodate a wide variety of V/U/SHF antennas.
>     We won't need a processor; the laptop will come with a processor much
>     faster than 40 MIPS.  (The current XO CPU is a Geode LX 433 MHz x86,
>     with MMX, 3DNow, and some SSE instructions.)

The OLPC chip is capable and can run a small dedicated sdr/dsp core to
do many functions.  I would like to see us offload stuff on to some kind
of helping processor so we could do more than just 5 kHz wide AM/SSB, or
NBFM, etc.
> We can argue that a "radio coprocessor" would greatly enhance the range
> of possibilities -- DRM (Digital Radio Mondiale) for example, and see
> below.
>     > We need a DDS and a QSD (we do not need the QSE for the receive only
>     > version) if we are going to tune the HF shortwave broadcast bands and
>     > get reasonable performance at low cost.
>     I think that single chips are available that do broadcast-band AM and
>     FM decoding for cheap; has nobody done this for the television and
>     shortwave bands?  Or is the problem that nobody's done this digitally?
> Two problems. One is that the off-the-shelf chips use proprietary IP.
> The other is that the off-the-shelf chips are locked up and it's next to
> impossible to do anything interesting with them that you can't already
> do with a cheap external radio. I'm not aware of commercial devices that
> could be used to capture and detect *all* of the signals within a 50 kHz
> bandwidth, which could probably be done with ease with the assistance of
> a radio coprocessor. This is an essential step towards "cognitive"
> functions -- make the radio functions mutable and dynamic.
>     If we can provide something that gives real benefit for the target
>     kids, we shouldn't be dogmatic about analog versus digital.
>     Alternatively, if OLPC provided a million-unit order for a digital
>     tuner chip that would target all these bands, others could then buy the
>     cheap chip for a variety of projects.
>     > This would provide a clear example of how it could be done.  It
>     does not
>     > meet the price point, but it shows the capabilities and then we can
>     > negotiate.
>     I'm glad you-all are pointing out low volume prototypes... 
> I'd think in part we'd be providing not just sealed up applications but
> also programmable devices and an API, capable of being used in
> innovative ways in software *without* requiring the chronic intervention
> of large-scale chip producers. Part of the SDR mission, isn't it?

Open Standards, open source, free infrastructure?  That is a little
radical isn't it?  Should that be our mission?

I certainly hope so.  That is my life's mission, which I am grateful in
the extreme that my employer is allowing me to pursue with a vengeance
and with (probably) more clout than I deserve. I am determined to help
end the repeated purchase of, and closed system support of,
infrastructure that should be available to all (and which we are tired
of paying for over and over and over).  With this freeing of resources,
we would be leaving the companies, individuals, governments, students,
WHATEVER, to innovate ON TOP of that already done infrastructure.  Think
of how much more productive the existing money pool would be if almost
ALL infrastructure code was free (operating systems, word processors,
spreadsheet, radio basic functions, etc.)  and we were not having
companies, governments, etc. repeatedly paying for the same closed
system infrastructure to be done as well as the huge support tail for
maintaining it. Then companies would be free to spend lots more of their
money on innovation, creativity, and more, held back then mostly by the
huge part that must go to lawyers to make sure they have a sufficiently
large patent portfolio to defend the innovation (Can we stop that next?)
 I just don't understand why all of the corporate, government,
educational, etc. world is not HOWLING for free, open standards based,
and preferably open source infrastructure code for almost everything and
the end of this closed system and amassing of patent portfolios spending
completely unproductive money (and more importantly time) on lawyers.  I
have two friends, one of them for about 25 years.  Both are brilliant
engineers, and are members of these mail groups.  One has a name that
will be known, and live long after he is dead and gone.   He is now
spending almost ALL of his time helping lawyers make the existing
corporate portfolio fit the "crime". It is an utterly ridiculous waste
of a great mind.

Sigh, don't get me really started. I might yield an opinion!

The second generation OLPC, which I hope is on the drawing board, should
have inexpensive radio, done by software in every way possible, to give
the OLPC recipient access to communications with the rest of the world.
   I suggest that we contact a few companies, such as Microchip and ask
how much for a dsPIC33 in quantity 1 million?  But we have the OLPC
going out the door today.  If it fails, I think OLPCv2 is going to have
a hard time going forward.  There are already "nay sayers" and
competitors with questionable agendas showing up.  If an inexpensive
external device could be done for the OLPC, using its existing
processor, that would be a very nice first step.   We could indeed build
a transceiver with that.  John's price point, power and size constraints
seems to limit us almost completely to a receive only device.  Maybe
that is as it should be but I just want that argued and accepted clearly
as the correct goal.  With the external device, done in quantity to
reduce costs,  we could more easily have a transceiver.  If that is not
desirable, then so be it.

Ordering from Digikey,  we could build an HF receiver interface using
QSD and a DDS plugging into the USB port on the OLPC for ~ $30 at
quantity 1500 with the most expensive part being the DDS and accounting
for nearly 1/2 of the cost.  That says to me that if we got the
quantities well up from 1500, we could get the price down significantly
but I just do not see it getting down to under $1.  We need to add SMT
based bandpass filtering.

Maybe a device like this one:


Done by this company:


could be made in large quantities at low cost but under $1?  I have my
doubts that it and others like can be unless some players in industry
are going to step up and provide these kinds of pieces to us.  For us to
succeed in the quest for the lowest cost devices, it is my opinion that
we have to find EXISTING technology, learn how to use it, and then try
to convince the owner/developer of the IP that there is a serious
business case for getting it to us cheaply.

> Regards
> Frank

Season's greeting to all and Happy New Year.
Bob McGwier

AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL,
“An optimist may see a light where there is none, but why
must the pessimist always run to blow it out?” Descartes

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