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Old 11th March 2013, 07:07 PM   #1
davada is offline davada  Canada
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Default CaptureWidget

This is a continuation of the discussion of a project based on the SDR-Widget and Audio-Widget. The project is a dedicated ADC-analog front end for the purpose of low distortion measurement. Continued from EMU0204 mods for FFT measurements.

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Old 11th March 2013, 07:12 PM   #2
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OK, I'm in! Thanks for doing this David!
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Old 11th March 2013, 08:01 PM   #3
RNMarsh is offline RNMarsh  United States
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And, I'm always interested in test equipment. Thx-RNMarsh
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Old 11th March 2013, 08:50 PM   #4
borges is offline borges  Norway
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Hi guys,

this is interesting. It is quite doable to add ADC capability to the Audio-Widget project (see my signature below). I can give my present AB-1.2 a respin with new analog features. And I'm sure it is quite doable to reuse SDR-Widget code for the ADC support.

BÝrge
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Old 11th March 2013, 09:24 PM   #5
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For those who are interested you can grab the document archive and BOM for the SDR-Widget from this page
Yoyodyne Consulting/SDR-Widget

The ADC support electronics are a compromise as it is powered from the USB bus but the performance is acceptable

The SDR-Widget supports some bells and whistles you may want to drop (I2C/quadrature encoder/LCD display)

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George
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Old 12th March 2013, 01:33 AM   #6
davada is offline davada  Canada
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Hi Guys,

I take it from Borge's statement that the Audio-Widget at present doesn't have the ADC capture support.

George the rotary encoder will be vary handy for an analyzer set. In fact four would be handy. But I going to leave this for a completely different project because there are mixed desires here for functionality. The LCD is a handy tool for debugging it could be dropped when it no longer serves a purpose.

If we can make this modular by grouping unused IO pins to some type of header that mates with a connector, cable or otherwise. Perhaps we can come up with something and call it universal. Something that would support add-ons or offer other bits of control. No pun intended there.

Before I go any further with this is there any available processing power left in the SDR/Audio-Widget? How much other functionality can the Atmel support?

I'm posting a PDF from AKM I'd like everyone to have a look at if you haven't already.It describes the parallel use of two or more ADC to increase dynamic range and lower the noise floor. There are a number of approaches to doing this and we need to decide which is the best way. I'd like to open a discussion on this.

I think to avoid something like an FPGA, which would be over kill, between the ADC and processor the I2S of the ADC's could be multiplexed.This would require a bit more processing overhead, a buffer to hold the words, some simple integer addition and a bitwise shift operation for dividing to complete the task.

http://www.akm.com/AppsNotes/AN120516.pdf


Cheers,
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Last edited by davada; 12th March 2013 at 01:37 AM.
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Old 12th March 2013, 04:10 AM   #7
1audio is offline 1audio  United States
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I had an good meeting with AKM some time ago and went over this application with Joel. He said that he could help with recommendations of suitable DSPs to do the necessary processing. They really are neither expensive nor power hungry. I'm using several in a Bluetooth headphone project now that can do 192 KHz or better running on 3.3V and using no power. We just need to be able to load the DSP code. I can get direction on either TI or ADI parts that can do this (and much more). We do not need FPGA's. They are nice but not necessary and way overkill in development for this application (and most audio ones today).

Look at the DSP's in this block diagram. Block Diagram (SBD) - Pro Audio Mixer - TI.com I'll check with TI to see which ones to use. There is enough power to do some processing in the DSP before it comes back to the system.

Also an option is the ADI Sigma Studio stuff: SigmaDSP Processors | Processors and DSP | Analog Devices
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Old 12th March 2013, 04:32 AM   #8
davada is offline davada  Canada
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Quote:
Originally Posted by 1audio View Post
I had an good meeting with AKM some time ago and went over this application with Joel. He said that he could help with recommendations of suitable DSPs to do the necessary processing. They really are neither expensive nor power hungry. I'm using several in a Bluetooth headphone project now that can do 192 KHz or better running on 3.3V and using no power. We just need to be able to load the DSP code. I can get direction on either TI or ADI parts that can do this (and much more). We do not need FPGA's. They are nice but not necessary and way overkill in development for this application (and most audio ones today).

Look at the DSP's in this block diagram. Block Diagram (SBD) - Pro Audio Mixer - TI.com I'll check with TI to see which ones to use. There is enough power to do some processing in the DSP before it comes back to the system.

Also an option is the ADI Sigma Studio stuff: SigmaDSP Processors | Processors and DSP | Analog Devices
What's available for development software for these DSP for free?
What I've seen from the manufactures is big $$$.
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Old 12th March 2013, 05:47 AM   #9
mkc is offline mkc  Denmark
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Hi,

What signal processing do you think that would be advantage to process in the ADC?

I would suggest just get the data transfered to the PC. A couple of years ago I was a part of a team that made a inhouse high-speed trace/sw debugger tool. We ran high-speed USB and transfered ~20 MByte/s sustained. We could let it run overnigt without any transfer errors. I have to add that we ran bulk-mode. I think the USB connection should be ok for getting the data to the PC and use the processing power of that crunch the numbers.

Best regards,
Mogens
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Old 12th March 2013, 06:00 AM   #10
davada is offline davada  Canada
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I guess we can't bit shift a two's compliment to divide. That won't work.
Yes even a DSP seems a bit over kill for a simple operation but they are cheap.
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