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Re: [Xylo-SDR] Earlier Wolfson vs TI Discussions



Errrr Ahhh Yes! I feel strongly all ways!


You are reflecting my sentiments. The end product does NOT have to be the Xylo, nor should it be. However as you mention, our development system should be open and as much the same as possible. They Xylo/Saxo already has the resources which we are likely to want, but not our initial overhead to develop them to get going. Do you already have the FX2 Fifo’s done? I2C? In the end, the development sytem can help our group effort as well as any individual or other group efforts are out there.


Yes, we should do our own ‘uniform’ boards.


I definitely like the mother/daughter scenario although it might be a little more expensive in the beginning. I had thought that a couple of 40 pin headers would be OK between slots on the bus. Includes Power 5, 12, Grounds, I2C from Xylo, I/O from Xylo, and interconnects between boards. Two times 40 pins with grounds in between each pin really is not enough. My thoughts are now turning to passive pciexpress buss. Not with the PCI standards connections but our own design. 12 volt power in, 5 V regulator, and as Phil C mentions, regulators (or not) on each daughter card. Daughter cards can be any project we think can go on one card. First might be Programmable A/D, D/A, I/O -, Other possibilities for cards, accurate freq standard slaved to UPS. SD Radio cards. Also allows other groups and interests to design standard daughter cards for experimentation. PCIExpress proto boards are available, also with proper design it could include a non FPGA SBC. Also if we go PCIExpress, standard enclosures are available.


Just thoughts, but an open basis for experimentation.


Yep, I think we have a large enough group to get a design and purchase going.


Eric – AA4SW





From: xylo-sdr-bounces@lists.ae5k.us [mailto:xylo-sdr-bounces@lists.ae5k.us] On Behalf Of KD5NWA
Sent: Thursday, December 15, 2005 9:29 PM
To: Xylo-SDR Discussion
Subject: 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:

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.
(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>
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

"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 ... "