Re: ball-hours

From	rickman <gnuarm@gmail.com>
Newsgroups	sci.electronics.design, comp.lang.forth
Subject	Re: ball-hours
Date	2014-10-17 14:03 -0400
Organization	A noiseless patient Spider
Message-ID	<m1rllj$d4$1@dont-email.me> (permalink)
References	(9 earlier) <caagkuF1v4jU1@mid.individual.net> <m1p626$nu5$1@dont-email.me> <caaokmF457jU1@mid.individual.net> <m1pe4h$lcl$1@dont-email.me> <cacmifFj1vgU1@mid.individual.net>

Cross-posted to 2 groups.

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On 10/17/2014 10:14 AM, Joerg wrote:
> rickman wrote:
>> On 10/16/2014 4:37 PM, Joerg wrote:
>>> rickman wrote:
>>>>
>>>> Each processor is very low power when running flat out, just 5 mW.  But
>>>> they almost never run flat out.  Because they are asynchronous they
>>>> spend most of their time stopped when they draw 0.0875 uW, yes, that's
>>>> less than a tenth of a uW for each processor or just 12 uW for the whole
>>>> chip.  The processors respond to stimuli in just nanoseconds, not 100's
>>>> or even 10' but single digit nanoseconds.
>>>>
>>>> Trust me, power will not be a problem with this part.  It is a very
>>>> different beast to program however.
>>>>
>>>
>>> I wonder how that company is doing. I read about their products years
>>> ago but never seen any in schematics and I get to see a lot of new stuff
>>> because some of my daily bread is EMC remedy.
>>
>> I think they are doing ok, but mainly because they have nearly zero
>> overhead.  They don't pay any salaries so no need for layoffs.
>>
>
> Wow. So they all work for free? How do they make a living?

I believe many of them are functionally retired and don't need to work. 
  Others work part time and do consulting.


>>>> Every problem in your design is asking for an FPGA.
>>>>
>>>
>>> Possible, but not sure yet. Maybe there is a bigger processor out there
>>> with real I2S/TDM and enough support by the manufacturer.
>>
>> Yeah, maybe.  You can go with one of the Cortex A processors like they
>> use in the Beagle board or Raspberry Pi.  Without the Linux OS they
>> should so a decent job.  They have floating point for your FFTs as well.
>>   That will help prevent too much rounding noise in the FFTs.
>>
>
> Except the Sitaras in QFP have been obsoleted. But I'll find something.

Yeah, it will be hard to find anything more powerful in QFP.  Normally 
they need a high pin count which requires BGA.  All of the higher end 
devices I have seen use external memory which pushes the pin count over 
the top for QFP unless you can find one in a 208 pin QFP.


>>>>>> What are the specs you need from the ADC?  Do you have numbers and
>>>>>> such?
>>>>>>     I think you mentioned a low drift with temperature.  The GA144
>>>>>> would
>>>>>> need to be compensated for temperature, but has lots of processing
>>>>>> to do
>>>>>> that.  :)
>>>>>>
>>>>>
>>>>> Five needed in total, 18bits or more, 48ksps, differential inputs, BW
>>>>> from DC to 15kHz, without phase jitter issues. DC-Offset can be handled
>>>>> via mux and SW-clamping as long as it won't jitter or drift around
>>>>> much.
>>>>
>>>> "phase jitter issues" and "won't jitter or drift around much" aren't
>>>> specs.
>>>
>>>
>>> What I mean is that ADCs on processors generally cannot hold jitter low
>>> enough to truly deliver a 96dB SNR. I found that even 12 bits on-chip is
>>> already a serious challenge.
>>>
>>>
>>>    18 bits of what exactly?  I have seen lots of devices with 24
>>>> bits but only 96 dB SNR.  Do you need 108 dB SNR?  You won't get that
>>>> from the GA144 ADCs at 48 kHz.
>>>>
>>>
>>> True 96dB across DC-15kHz would be enough.
>>
>> So a 16 bit part with DC coupling would be good enough?
>
>
> No, because ENOB counts and there you need around 18 bits.
>
>
>>                                                ... The market is
>> *littered* with those.  I've seen a bazillion 18 bit SAR parts out
>> there.  Even LT has them, your favorite company.  Why not use one of
>> those?  They often have fantastic SNR and THD specs.
>>
>> How about an 8 channel, 16 bit ADC in one package?
>>
>> http://www.linear.com/product/LTC1867L
>>
>> Well, maybe not.  The SINAD is not so good.  What is the frequency of
>> the signal you are looking at?  The ADC specs also depend on your input
>> frequency.
>>
>
> DC to 20kHz but that requirement can be dropped to 10kHz. Also, if I
> really, really had to, I could replace one of the two DACs with a DDS
> chip because that just generates a sine wave. But it complicates the SW
> because such chips need their own SPI sermons in Swahili.

I don't see a DDS as being much more simple than a DAC with a lookup 
table.  What varies on the sine wave?  Does it have a slight frequency 
variation or amplitude?


>> The point is that if you can drop the I2S interface you have a lot more
>> potential MCUs to choose from.
>>
>
> Sure, if the CPU can manage to keep seven balls in the air and serve all
> those SPI device at 48ksps.

I have no idea why you think that is a problem.  This isn't juggling. 
This is electronics design and driving data over a few SPI ports that 
can all be managed though one port is not at all hard.  I think you are 
missing the "CONVERT" signal.

-- 

Rick

Thread

Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-15 00:25 -0400
  Re: ball-hours bruce.person@gmail.com - 2014-10-14 23:51 -0700
    Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-15 03:15 -0400
  Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-15 05:36 -0700
    Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-15 16:22 -0400
      Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-15 16:12 -0700
        Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-15 22:48 -0400
          Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-16 11:21 -0700
            Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-16 15:24 -0400
              Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-16 13:37 -0700
                Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-16 17:42 -0400
                Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-17 07:14 -0700
                Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-17 14:03 -0400
                Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-17 12:03 -0700
                Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-17 15:23 -0400
                Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-17 12:44 -0700
                Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-17 18:37 -0400
                Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-16 20:59 -0400
                Re: ball-hours albert@spenarnc.xs4all.nl (Albert van der Horst) - 2014-10-17 08:43 +0000
                Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-17 13:53 -0400
                Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-17 07:50 -0700
        Re: ball-hours Raimond Dragomir <raimond.dragomir@gmail.com> - 2014-10-15 20:42 -0700
          Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-16 01:50 -0400
            Re: ball-hours Raimond Dragomir <raimond.dragomir@gmail.com> - 2014-10-16 00:49 -0700
              Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-16 05:14 -0400
            Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-16 11:58 -0700
        Re: ball-hours "Elizabeth D. Rather" <erather@forth.com> - 2014-10-16 08:32 -1000
          Re: ball-hours rickman <gnuarm@gmail.com> - 2014-10-16 15:32 -0400
          Re: ball-hours Joerg <news@analogconsultants.com> - 2014-10-16 13:45 -0700

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