ball-hours

So I guess they are hoping the company some day lands it big, their equity stake turns into pure gold and then they can buy a Cessna Citation with a matching tropical island :-)

It would be nice not to need external memory. Don't want this to turn into a monster with an RTOS, its own government and all that.

... The market is

The sine wave is constant in normal operation, except during a sweep phase at the start. So a DDS would greatly cut down on data volume. During operation it would not require any data sent over the SPI.

I know how the hardware goes, done a ton of SPI designs with synchronicity requirements and they all work. What I am concerned about is the barrage of data inside the CPU that wants in and out. Something in there has to slosh that around. AFAIU in a TDM scenario it would simply flow nicely in a serial fashion. But that's where I'd have to hand it over to SW experts because I am not a programmer.

I think they are just along for the ride and trying to have fun.

There is nothing about a processor that requires an OS. It is the system requirements that determine if an OS is needed.

I can assure you that what you are calling a barrage of data is nothing to even give a second thought to. Remember, you are performing a multiple 1024 point FFTs every 256 samples. I expect the processor impact to be at least a 10:1 ratio not even counting the other processing you need. Handling the interface will be in the noise as long as you aren't bit banging.

Why not? I can't imagine this being much fun but I am not a processor guy so I can't judge that.

I know. Should have placed a smiley. I just meant that I don't want this to turn into a major science project.

A 100MHz ARM would be loaded to 50% with all the FFTs and other calcs running. So if the SPI takes up another 20% we'd still have sufficient reserves. I don't like to go past 70% on CPU load becasue there will always be some sort of feature creep.

Handling the interface will be in the noise as

Well, let's hope so. In that case we could use any SPI ADC/DAC. But most are audio so they come in I2S fashion. There isn't much out there in generic converters once you need 18 bits or more.

If I were doing this I would just go with the Blackfin and forget the ARM. The Blackfin is a DSP device with lots of support for doing DSP. It has much more performance and the only down side I can see is that it needs an external flash for program store.

Are you kidding? Did you look at the ADI link I posted? ADI makes dozens and I believe TI makes just as many up to 20 bits and more. There is a market segment that matches the technology in SAR devices called "control". Sound familiar? They don't need to be as fast as flash converters and so can be made much lower power while still achieving MSPS rates. The market for audio is a lot bigger, so the audio portfolios are larger.

The big disadvantage for control of most audio devices are the large delay times of the digital filters required to make sigma-delta conversion work. It seems your application doesn't have that concern.

I think the AD1939 has around 0.5 ms delay, that is each way both ADC and DAC. Also many of them are AC coupled. I use an AKM part on the board I produce and they work just fine, but no DC path. This is an audio app so it's fine.

Here is a link for TI showing 24 potential ADCs. Some of them are up to

Here is the link for ADI parts of 18 bits at 48 kSPS

not a huge issue it can boot from a serial flash, so it's a $1 part in SO8

running from a parallel flash would be dog slow

The ones I've seen and used from ADI very expensive compared to the ones targeted audio

-Lasse

I found that if you need true 16-bits ENOB at full audio sampling it gets even more expensive. Also a bit cumbersome to set up. I2S/TDM would make life much easier.

Right now I am looking for the path of least resistance (least engineering effort), not so much cost. So Blackfin demo boards or whatever would be fine. Later in the product cost will matter and then there is an advantage if the conceptual design was already targeted towards a lower cost audio solution.