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Re: [Xylo-SDR] Earlier Wolfson vs TI Discussions
Eric are you trying to be Santa and the Grinch at the same time? Split
personality maybe? :-P
I want to play with the Wolfson chips, but I agree with Phil that the TI
chips are a more practical way to go. Next week I'll be trying to acquire
a set of the TI chips and the associated parts to make the thing
fly.
Many of the points he made need to be discussed, so maybe Friday or
Saturday we can all chime in. The reason I bought a Xylo, is not because
I think that is what we will end up with, but as a training vehicle so I
can learn to program the Altera chip along with the group. At some point
we need to come up with a strategy of what the board will have, what is
on what pins, ... etc, so we don't end up heading in different directions
and different boards.
My preference would be as a group come up with a set of specs and have
the board made and available so all that wish to participate have exactly
the same hardware, and we can exchange programs with each other.
I really like the mother/daughter board arrangement because it makes the
FPGA card, and a separate A/D, and D/A useful devices for multitudes of
projects, let them talk to each other through I2C cable. This arrangement
makes easier in the future to upgrade the part that needs it without
throwing away everything.
I am convinced that if we create our own board it should be with the
Cyclone II parts, the smallest member has 2X the speed, 2.5X LEs, 3X RAM,
2X PPL, 13 multipliers, and only cost $2 more than the Xylo chip in Qty
1.
Anyway enough ranting, I'll save it for the Teamspeak or Xylo
forum.
At 05:39 PM 12/15/2005, you wrote:
Folks
Checked back and it was almost exactly a month ago when Phil_Harman ?
VK6APH mentioned his early experiments with the Xylo and his student. MAN
has this little group moved fast!
In spite of the fact that I will be sending out the Wolfson chips to as
many as I can. Phil Covington ? N8VB posted an excelling rebuttal of the
?Wolfson Decision? and had done quite a bit more research into A/D and
Codecs after Phil_H?s and our search last Spring. The TI chips are
readily available, inexpensive and do some other things that Wolfson does
not. I am republishing that early conversation, since the TI chips ARE
the way to go if this project indeed is to eliminate reliance on
commercial sound cards for SDR in any implementation. (Ahti?s comments
re: do it all in the FPGA, not withstanding).
I am republishing that somewhat limited distribution conversation here
for reading. Phil_C makes the point and I sure have been convinced. I
also intend to order up the TI stuff. I am not trying to quash any
experimentation. TI is the way to go in the future. All things even being
equal (which they are not) the availability of TI stuff turns the
tide.
**************************************************************************************************************************************************************
SNIP
(Phil Covington?s rebuttal)
I feel very strongly about this so I will offer the following
argument:
<argue mode>
I could understand staying with the Wolfson parts if the design was
finished, the parts easy to get, or they had some compelling performance
advantage. If you were only talking about building one or two
projects for yourself it wouldn't make much difference either.
Unfortunately the parts are difficult to get and do not offer any
performance advantage. The PCM4202 is equivalent or superior to the
WM8785, readily available (in stock at Digikey), and there is a twin
PCM4204 part which gives you 4 channels instead of two - if more
channels are ever needed. The WM8971 does not offer any
compelling
advantages either - the TI 24 bit CODEC TLV320AIC23B gives you *all* that
the WM8971 has and more. It also has two DACs with PGAs and output
drivers right on the chip. The WM8971 is only an ADC - you will
need to add a DAC whether it is an external chip or it is done with PWM
in the FPGA. It would be much easier to just use the TLV320AIC23B's
DACs. The TLV320AIC23B is in stock at Digikey now.
Samples can be ordered from TI's website.
</argue mode>
http://focus.ti.com/lit/ds/symlink/tlv320aic23b.pdf
I have researched a lot of ADCs, DACs, and CODECS, comparing their specs,
availability, etc... I have samples of all of them except the AKM
parts.
Cecil Bayona
KD5NWA
www.qrpradio.com
"I fail to see why doing the same thing over and over and
getting the same results every time is insanity: I've almost proved it
isn't; only a few more tests now and I'm sure results will differ this
time ... "