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 Posted: Feb 15, 2011 - 06:16 AM |
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Joined: Aug 19, 2002
Posts: 17
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Has anyone managed to setup the ADC in the Xmeag128A1 for single ended 12 bit operation. I would like to get 0 to 4096 bits. All of Atmels single ended examples are differential inputs which gives half the resolution.
The data sheets are not clear as to which registers to set. The ASF and example codes are different. The examples use two different drivers, ADC_driver.c and ADC.c. Not sure why.
Sample code would help. |
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Posted: Feb 15, 2011 - 07:33 AM |
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Joined: Nov 28, 2004
Posts: 3552
Location: San Diego, Ca
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All I have is this:
http://blog.frankvh.com/category/electronics/ |
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Posted: Feb 15, 2011 - 08:07 AM |
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Joined: Dec 01, 2003
Posts: 2502
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| Search the forum for adc and xmega, and try what I did |
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Tom Pappano
Tulsa, Oklahoma
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Posted: Feb 17, 2011 - 03:27 AM |
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Joined: Aug 19, 2002
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tpappano wrote:
Search the forum for adc and xmega, and try what I did
Hey Tom,
What did you try?
I have pretty managed to get most modes running using the examples, but the single ended unsigned mode has eluded me. Oh for 4096 bits.
I am still waiting for a reply from support.Atmel.no ,but it looks like from what I have read on blogs that this option may be wishfill thinking. |
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Posted: Feb 17, 2011 - 04:37 PM |
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Joined: Dec 01, 2003
Posts: 2502
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Try doing this, it will give you a 4096 count single-ended behavior and good performance. (do let us know if the latter proves true for you)
Quote:
From the "XMega ADC Question" thread:
Quote:
I'll save you some pain, it will work this way:
Use external 1.22v (or thereabouts) reference
Use differential input mode
Route "-" differential input to 1.22 Vref (using mux options)
Read result as "signed"
The adc range will be 0-(Vref*2) volts
Apply whatever math you need to correct gain and offset, and create whatever numerical presentation you want.
Let us know if this seems to work for you. There will likely be a small offset (maybe ~20 counts) that needs to be compensated arithmetically, and which may prevent you from reading the first couple mv above ground, unless you do a slight external level shift with a couple resistors.
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Tom Pappano
Tulsa, Oklahoma
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Tom Pappano
Tulsa, Oklahoma
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Posted: Feb 19, 2011 - 05:22 AM |
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Joined: Aug 19, 2002
Posts: 17
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The PCB is finished. I cannot fit an external Vref. I am also waiting for answers from Atmel support. The last answer was to use the AVR1300 example. I cannot see the example doing 12 bits single ended. I have tried them.
I am starting to believe there is a hugh problem with the Xmega ADC. I am not sure why Atmel support are so silent about it? |
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Posted: Feb 19, 2011 - 08:41 AM |
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Joined: Dec 01, 2003
Posts: 2502
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| If you want to get 12 bits and usable accuracy, you may have to glue a reference on somehow, or redo the board. The data sheets detailed a lot of the adc problems, but sadly the descriptions of the adc operating modes seemed like gibberish to me. That 11 bit nonsense didn't show up until I actually wired one up and tested it. |
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Tom Pappano
Tulsa, Oklahoma
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Posted: Feb 19, 2011 - 08:41 PM |
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Joined: Oct 30, 2008
Posts: 333
Location: Minnesota, USA
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indianajones11 wrote:
Wow! It's like you have an auto reply set up whenever someone posts with the words 'xmega' and 'adc' 
Really nice on the blog though. It saved me a LOT of time, that's for sure. I think my solution is to just tie a clean 2V signal into the VREF pin.
rodl wrote:
The PCB is finished. I cannot fit an external Vref.
That really sucks. Can you reorder? |
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Posted: Mar 03, 2011 - 11:39 AM |
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Joined: Aug 19, 2002
Posts: 17
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It does seem Atmel cannot do what it says in the manual that it can do. I have dropped the Xmega ADC for a trusted mega ADC. When I have some time I will add a external vref.
Thanks for all your help. |
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Posted: Mar 03, 2011 - 03:27 PM |
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Joined: Sep 17, 2006
Posts: 12
Location: Malaysia
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Hi,
Is the problem with XMega ADC solve.
I am also about to kick start a project using XMega and ADC.
M.Pathma |
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Posted: Mar 04, 2011 - 12:05 PM |
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Joined: May 27, 2010
Posts: 396
Location: The land of Cyrus the Great
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Pathma wrote:
Hi,
Is the problem with XMega ADC solve.
I am also about to kick start a project using XMega and ADC.
XMEGAs have still some resolution problems. What are your resolution and conversion time requirements? |
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Ozhan K.
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Posted: Mar 27, 2011 - 12:34 PM |
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Joined: Sep 17, 2006
Posts: 12
Location: Malaysia
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Hi, Electronic Designer,
After reading all the issue on Xmeage, I took in some Xmega board from MikroE, I was unit release ID :7, which should be stable.
So far I did not see any major issue on this chip, I am using BASCOM-AVR, have not played with AVR-GNU.
My management decide to go with PIC24FJ for this project because worry of the stock and hidden issue.
Atmel should really concentrate the 100s and 1000s customer base.
Honestly, as Product Developer, I love XMega, it has the possibility to be the defector chip in our design needs. If Atmel can ensure the low volume supply stability like PIC.
M.Pathma |
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Posted: Mar 27, 2011 - 02:22 PM |
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Joined: Jul 18, 2005
Posts: 62320
Location: (using avr-gcc in) Finchingfield, Essex, England
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Quote:
Atmel should really concentrate the 100s and 1000s customer base.
Why? They probably sell more AVRs to their top ten customers than the rest of the world combined - it's their needs they'll concentrate on. |
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Posted: Mar 28, 2011 - 12:23 PM |
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Joined: May 27, 2010
Posts: 396
Location: The land of Cyrus the Great
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clawson wrote:
Why? They probably sell more AVRs to their top ten customers than the rest of the world combined - it's their needs they'll concentrate on.
And what about responsibility? |
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Ozhan K.
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Posted: Mar 29, 2011 - 03:24 AM |
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Joined: Dec 01, 2003
Posts: 2502
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Quote:
And what about responsibility?
Atmel's primary (and, practically only) responsibility would be to their stockholders. |
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Tom Pappano
Tulsa, Oklahoma
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