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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 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. ************************************************************************************************************************************************************** Hi Eric, On 12/5/05, ecellison
<ecellison@comcast.net> wrote: > Phil > > Great going. I think
PhilH, (and I agree) will stay with the Wolfson. > Also will use the
Wolfson 8971 for general purpose mic in, with ALC, > and speaker out, simple
I2C interface. Parts in volume about 6 bux but > who knows. I called
local ( > 10 samples of 8785's.
Had not heard anything as of today, but will > call tomorrow and also
inquire about the 8971. I think that if we > develop a 'product'
based on these chips, we will be able to get > hundered quantities or
more. I think they have distributors in GB and > (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. > As long as the
"Xylo-Phreaks" have enough to test and develop on I > think we will manage to
gettem in any end product. I offered my Xylo > to PhilH however
apparently he is getting a replacement. BTW: they are > out of Xylos till Feb
or so, which puts a quash on our group if it > grows more. Dale has
created an SVN for this project on Hamsdr.com. > However, neither Phil
nor I (or others?) know how to get a project > like this going and how
it will work. Perhaps you can help since I > know you have done
project management like this. PowerSDR is also going on there. When there is some code to
check in, send it my way and I'll get it into SVN. I just need to get
Dale to set up a user name and password (we will all need them for
development). On PowerSDR: We were considering Berlios until Dale offered
to host the projects on Hamsdr which is a great thing as far as speed and
availability. I am very happy that PowerSDR development will be done
through SVN - I think a lot of people have been holding back because of
the difficulty of coordinating PowerSDR development. > PhilH asked if I would
do a circuit board based on the Wolfson 8587. > Then we discovered the
8951 or 8971 and also thought we should put I2C > 16 bit Microchip 23016s
on the board. Feature creep went rapidly and > pointed to the problem
of not having an interchangeable hardware system capable of updates. > My thoughts are to
create a 'motherboard' and buss structure board > with perhaps 40 pin
.100 pins as on your board. Include analog and > digital regulated power
12, 5, 3.3 and 1.2v and run the I2C, user > assignable Xylo pins,
and I2C busses clks on the mother board. Watcher think? Since we are using 24 bit
ADCs in an attempt to get high dynamic range, it may be better to put only a 12
and 5 V supply on your motherboard and do the lower voltage regulators on the
ADC board(s). Where will the FPGA reside
and will you stay with the Cyclone (and which part)? - assuming that you will
not use the Xylo board in the final design. If you are going to make this
into a project (as opposed to a couple of units for personal use) I would highly
recommend that the Xylo board is not a part of the design. (Lack of)
Quality problems alone with the Xylo will cause it to be a nightmare for
users. The Xylo board is very easy to duplicate but is fine for
development use. Altera is the way to go. The
only reason I used the XILINX Spartan 3 in my project s that it has 18 bit
multipliers which makes certain things much easier and faster when you want to
do the DSP in the FPGA. I would have much
preferred to use an Altera FPGA otherwise since they are much easier to get. > I'm willing to > invest the time to
learn to layout the stuff in ExpressPCB or other, > since I am not a
programmer and will probably be an 'assistant' where I can help. This is where I would
STRONGLY recommend that the schematic and PCB stuff be done in an open source
tool. If the design files are going to be shared then it does no good to
have a "open" hardware project using closed or proprietary
$$$ tools. Sometimes there is no choice, but in the EDA end there
is. Using ExpressPCB locks people into using their service if they want
to duplicate the boards. Luckily the Altera and Xilinx design tools are
free for download. I would recommend either
gEDA or Kicad. IMO, Kicad is much easier to use and more polished of the
two. I have used PADS, ORCAD, Eagle, etc... and Kicad feels more like the
professional tools. I have the full blown $$$ version of PADS logic and
PADS layout here for my paying projects, but I plan on doing all my open
hardware PCB work in Kicad. The free but limited version tools such as
Eagle are an aggravation in the end - you always run into the size limits
eventually. Now if you think that no one
would be interested in duplicating the design themselves then ExpressPCB would
be ok. > That way we can add
'daughter' cards interfaced to the Xylo. The board > can be placed down on
the CONIO1 pins. In the end the entire prototype > system could be a
product external to the SDR-1000. The Xylo also > gives us graphics
display capability etc. With the motherboard and
other daughterboards you are not too far away from just replacing the SDR-1000
especially for RX only use. All you really need to do is add the QSD on
the ADC board and design a DDS board :-) > In any case, I have
lost track of all the xylo owners but know a few > and will put together a
mailing list. > > Eric Maybe we can ask Dale to
create a Xylo section on his Hamsdr forums? 73 de Phil N8VB |