Wide frequency range, arbitrary waveform DDS

On Tuesday, August 23, 2022 at 10:59:51 AM UTC-4, Stef wrote:
> On 2022-08-22 gnuarm.del...@gmail.com wrote in comp.arch.fpga: 
> > On Monday, August 22, 2022 at 4:24:41 AM UTC-4, Stef wrote: 
> >> On 2022-08-20 gnuarm.del...@gmail.com wrote in comp.arch.fpga: 
> >> > On Friday, August 19, 2022 at 6:45:53 AM UTC-4, Stef wrote: 
> >> ... 
> >> >> I think it is obvious. Phase accumulator points to LUT, but LUT isn't a 
> >> >> sine table but sommething else. 
> >> > 
> >> > Yes, it is obvious. That's why I'm asking what you are looking for from this discussion. 
> >> In my original post, I had 2 questions 
> >> 
> >> 1) Are there objections to using a prescaler and a shorter phase 
> >> accumulator for generating frequencies over a wide range? 
> >> 
> >> This has been discussed. Conclusions is that you should keep the 
> >> accumulator as long as possible for best performance. 
> > 
> > If any of that is from my comments, I retract them. I was thinking of a typical DDS generating a sine wave.
> Most of those comments (and of Waldek) will also apply to AWG in some 
> way, so no need to retract. Also the output filter argument is one 
> against switching sample frequency. Ofcourse I can keep the pre-scaler 
> option in mind, but I don't think it should be the initial approach. 
> Only an optimization when really necessary (speed, size, etc).
> > You only need the clock rate to suit the waveform you are generating, such as Nyquist considerations. Your memory is finite, so you have a fundamental trade off between clock rate and duration of the AWG pattern. I don't know your real requirements, so I can't advise you about how to optimize this. It will depend on your particular problem. 
> > 
> > 
> >> 2) Are the complete DDS chips available that have a downloadable LUT, 
> >> instead of the standard sine table? 
> >> 
> >> If such chips are available, I may not have to develop a custom 
> >> (FPGA/CPU/DSP) solution. This question has not been answered and I have 
> >> found non myself sofar. 
> > 
> > Yeah, I've never used DDS chips, so I couldn't say. As I've mentioned, there are many AWG products at other levels of integration, modules and boards. eBay abounds with them. 
> > 
> > 
> >> > I don't know what your requirements are, but you can buy low cost AWG board level products and small box level products. 
> >> At this time there are only general requirements (AWG, 12MHz BW, ...). 
> >> If the project continues, this will be detailed further. 
> >> 
> >> Do you have an example of such a board level product? If it can do what 
> >> will be required, it is certainly an option. 
> > 
> > Try punching AWG into eBay or one of the other sites.
> Searching on AWG alone will find you a lot of wire. ;-) 
> With "arbitrary waveform generator", I get a lot of complete bench top 
> generators. And a number of (usually the same) cheap bare board units 
> like this one: 
> https://www.ebay.com/itm/221506533974?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=MRtVGD4USYW&sssrc=2047675&ssuid=&widget_ver=artemis&media=COPY 
> 
> This one is 8-bit 256 sample 100 kSPS. Not enough on every parameter and 
> it seems most of these modules have similar specs. 
> 
> But this is the kind of board level product you meant? I hoped for 
> someting that can be placed on a board. Looks like I need to implement 
> something myself if this project continues. 

There are products out there that do exactly what you want.  I found Bitscope, for example, which seems to have a board level product, but their web site is so goofy I can't find actual specs on it.  The control panel example they show only provides standard waveforms, not arbitrary.  So I'm not sure it is an AWG.  

http://bitscope.com/product/BS05/

You might need to contact them. 

How many do you need?  Is it worth the effort to roll your own?  How are you going to provide a waveform input/definition? 

-- 

Rick C.

+-- Get 1,000 miles of free Supercharging
+-- Tesla referral code - https://ts.la/richard11209

On 2022-08-23 gnuarm.del...@gmail.com wrote in comp.arch.fpga:

...

> There are products out there that do exactly what you want.  I found Bitscope, for example, which seems to have a board level product, but their web site is so goofy I can't find actual specs on it.  The control panel example they show only provides standard waveforms, not arbitrary.  So I'm not sure it is an AWG.  
>
> http://bitscope.com/product/BS05/
>
> You might need to contact them. 

Indeed a bit goofy, found no specs either. They say arbitrary but only
show standard and distorted standard waveforms. Also no indication how
to get truly arbitrary data in.

> How many do you need?  Is it worth the effort to roll your own?  How are you going to provide a waveform input/definition? 
>

Number is still unknown (to me), but it is for a commercial product. So
just sticking in some fancy boards will not be an option. There will be
more generators and signal operations and a lot of other stuff, so it
will be custom board(s) and controllers etc. anyway. And then you have
things like form factor and design and more. The AWG bit may in the end
be the simplest problem to solve.

Getting the data in is another thing completely and that will probably
involve PC programs and cloud connections. Not my first choice, but
understandable from our customer and end user points of view.

-- 
Stef

Windows - From the people who brought you EDLIN!

On Tuesday, August 23, 2022 at 12:47:35 PM UTC-4, Stef wrote:
> On 2022-08-23 gnuarm.del...@gmail.com wrote in comp.arch.fpga: 
> 
> ...
> > There are products out there that do exactly what you want. I found Bitscope, for example, which seems to have a board level product, but their web site is so goofy I can't find actual specs on it. The control panel example they show only provides standard waveforms, not arbitrary. So I'm not sure it is an AWG. 
> > 
> > http://bitscope.com/product/BS05/ 
> > 
> > You might need to contact them.
> Indeed a bit goofy, found no specs either. They say arbitrary but only 
> show standard and distorted standard waveforms. Also no indication how 
> to get truly arbitrary data in.
> > How many do you need? Is it worth the effort to roll your own? How are you going to provide a waveform input/definition? 
> >
> Number is still unknown (to me), but it is for a commercial product. So 
> just sticking in some fancy boards will not be an option. There will be 
> more generators and signal operations and a lot of other stuff, so it 
> will be custom board(s) and controllers etc. anyway. And then you have 
> things like form factor and design and more. The AWG bit may in the end 
> be the simplest problem to solve. 
> 
> Getting the data in is another thing completely and that will probably 
> involve PC programs and cloud connections. Not my first choice, but 
> understandable from our customer and end user points of view. 

lf you want to provide a very large memory, you can attach an SDRAM to an FPGA and have literally GBs of RAM at very high sample rates with low cost.  If the rest of the design does not require a large FPGA, you can do this is a small FPGA for less money than the memory chip.  

-- 

Rick C.

+-+ Get 1,000 miles of free Supercharging
+-+ Tesla referral code - https://ts.la/richard11209