RE: [Discuss-gnuradio] Hardware costs

[Mike]

With regard to using a BT848 or BT878 chip...

I haven't written any code using the BT848/878 chips, but I did spend
some time going over the spec sheets with the idea of raw analog
sampling in mind.  While there is no doubt that some great hardware is
built into the chip, accessing the raw data stream is the problem.  The
raw data gets manipulated significantly before it can ever get to the
PCI bus.  Further, injecting sync pulses would be necessary, at a
minimum, to be able to trigger certain parts of the chip.  There also is
the issue of the chips' UltraLock(tm) technology, which is used to lock
onto the horizontal sync signal to stretch and squeeze the data so every
horizontal scanline has the same number of pixels.  There are also
features such as filters, etc. that are great for video, but I can't
imagine would be good for sampling a generic swath of RF spectrum.  

There certainly are a number of great things about cards built with
these chips-- not the least of which, in my opinion, are that they're
cheap and most have tuners on them.  For anyone looking to work on an
implementation with one of these, I'd recommend also looking at the GPIO
port-- it's a high speed 24-bit wide digital IO port-- you lose the
built-in high-speed A/D converters, but might be able to keep the
high-speed data acquisition part of the card, which is significant.
It's intended for inputting digital video streams.  The datasheet
doesn't go into great detail into how to configure this part of the
card, so some research will probably be necessary for this approach.

There might be some tricks that could be played with, say, the svideo
input by putting the RF signal on the chroma channel and putting the
appropriate sync pulses on the luminance channel. 

BT878 and BT848 datasheets can be easily found by searching on Google.

Another thought might be to look at other commodity video chips to see
if any of them would be more suited to generic analog data acquisition.


-- Mike Turvey


-----Original Message----- 
Sent: Thursday, March 13, 2003 6:52 PM
To: 'Joel Konkle-Parker'; address@hidden
Subject: RE: [Discuss-gnuradio] Hardware costs

> So please, answer me this: what average, consumer-level good 
> is GnuRadio 
> if it requires a $1300 analog-digital converter card to work? 
> Are there 
> any alternatives I could use to get started with this?


GNURadio does not require any hardware at all, other than a computer
running
a POSIX OS.  Data sources/sinks can be files, random numbers, whatever.

If you want to do actual radio communication, you need hardware.  The
hardware that you need depends on the type of application you have.
GNUradio works with any hardware you can get a linux driver for.  

If you want to do narrow band stuff, all you need is a soundcard.  If
you
want HDTV, then the only option available now is a $1300 card.  People
are
working on cheaper options.  Your help would be appreciated.

BTW, somebody really should look into tweaking the BT848/878 drivers to
do
raw sampling.  It would get us 8-bit, 30+MHz sampling for about $30!  If
you
don't know what I'm talking about, read the archives from about a year
ago.
If you're actually interested in doing the work to make that happen, let
me
know.

Matt



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