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Re: ball-hours

Cross-posted to 2 groups.

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rickman wrote:
> On 10/17/2014 3:03 PM, Joerg wrote:
>> rickman wrote:
>>> On 10/17/2014 10:14 AM, Joerg wrote:
>>>> rickman wrote:
>>>>>
>>>>> 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.
>>>
>>
>> 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 :-)
> 
> I think they are just along for the ride and trying to have fun.
> 

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


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

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

[...]

>>>>> 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.
>>>
>>
>> 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 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.  


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
> long as you aren't bit banging.
> 

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.

-- 
Regards, Joerg

http://www.analogconsultants.com/

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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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