Re: arm7 core with fast monolithic 12-bit ADC

On Thu, 12 Feb 2009 10:19:14 -0800 (PST), rickman <gnuarm@xxxxxxxxx>
wrote:

On Feb 12, 5:30 am, korenje <kore...@xxxxxxxxxxx> wrote:
On Feb 12, 9:46 am, Jon Kirwan <j...@xxxxxxxxxxxxxxxxxxx> wrote:



On Wed, 11 Feb 2009 23:20:12 -0800 (PST), -jg

<Jim.Granvi...@xxxxxxxxx> wrote:
I'm seeing towards $4. But then I won't really know until an order is
placed. Can you say anything about the tool chains you've experienced
for this device? Cost, support reponsiveness, etc. Alternative
development tools you looked at but didn't actually wind up trying
out?

Not on this family yet, but I did like the look of the Peripheral mix,
so it is on our radar for future use...
.
Very fast ADC, and high resolution timers.

Yeah. I'm impressed.

TI are pushing some low-cost stuff
Experimenter Kit w/ControlCARD I see in stock at Newark for ~$82,
Piccolo controlSTICK is a USB stick, for $40.50

so that would be an easy way to quickly try the latest tools ?.

I suppose so. I'm a little disappointed looking at Eclipse
development tool costs for active development (not trial stuff.)
That's kind of off my radar range, if I decide to go that way. Which
means I need to dig a little deeper about tools. But yes, the device
appears attractive to me and I definitely appreciate the pointer. I
think I'd heard the name dropped here once or twice, but never took
notice before. But my head is turned now. So I'll put a little
effort into looking further.

Jon

Be vary, that F28xx (including the picolo family) internal ADC does
not deliver the promised 12 bits. Event the TI acknowledge this and
state thet the ENOB is around 10 bits (that was for the first members
of the family the F2812). For more info on this take a look at
comp.dsp and comp.arch.embedded archives and TI forumhttps://community.ti.com/forums/t/3165.aspx

The TI improves the ADC module each generation, but I can not tell you
how the picolo series ADC behaves

There are actually few ADC that give you the same number of effective
bits as resolution.

I never imagined differently. Resolution is almost a waste to care
about. The only thing it does is provide a __suggestion__ about the
care they took in designing it.

Any noise at all causes a loss of effective bits
and every part has noise, even separate ADC chips.

I know.

It is just a
question of how many bit survive the journey through the chip. 10
ENoB is not at all bad for a low cost 12 bit ADC, especially in an
MCU.

I know that isn't bad. In fact, as I mentioned earlier, my
expectations are only for about 10.5 bits ENOB, 65dB SINAD. I'm not
expecting the impossible here. Just something that isn't garbage.

If you need much better than that, you are unlikely to find it
without using a higher bit resolution device.

Which, obviously, would mean "slower" when talking about monolithic
designs with the microcontroller. It's the combination of speed and
ENOB that I'm looking for in a monolithic design and frankly I think
it isn't entirely out of the ballpark. It's a doable, not unreasoned
goal I'm looking for.

But as others have said, uncorrelated noise can be averaged out...

Obviously. Gaussian distribution (integral of Poisson) is the
assumption that goes into the very idea.

*if* it is uncorrelated.

Of course. Correlated noise violates the assumption.

It is common for the noise to be related to the clock.

Indeed.

After all, the same master clock is driving the MCU and the ADC.

I know.

I might expect this kind of lecture had I asked for something crazy. I
didn't. Perhaps someone else learned something, though.

Jon
.

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