Virtual channels, or not?

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Hi

 

I want to use all 16 ADC channels on the ATXmega384C3. All channels will be used to sample the same type of signal and range, i.e. they will all use the same setup.
Does that mean that I am not in need of the virtual channels? 

 

I can just use one virtual channel and change the input pin used for that channel, just as well as using four virtual channels, and changing those pins?
Or am I missing something?

 

Thanks,

 

   Thomas

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I think you're missing something...  What are these virtual channels you are talking about?

Greg Muth

Portland, OR, US

Xplained/Pro/Mini Boards mostly

 

Make Xmega Great Again!

 

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I don't know about virtual channels.  It's been a long time since I worked on ADC.

 

Xmegas, at least the AU, can perform conversions on multiple channels simultaneously.  So if you need all the speed you can get, that would be the way to go. Otherwise, do what's easiest.

Last Edited: Sun. May 31, 2015 - 07:54 PM
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Hi Thomas,

 

of course you can use ANY SINGLE virtual channel to measure all 16 physical pins.

 

Several virtaul channels are used in more complicated measurements, for example when you need to measure 2 different pins at exactly the same time (not one by one).

 

I have never used XMEGA C but you should be aware that XMEGA A has some interesting issues.

 

1. You should always use external voltage reference (that is 15 pins only left in your case)

2. This reference should be no more than VCC-0.6V, thus 2.5V or less

3. Single-ended measurement is less accurate compared to differential measurement when some extra pin is tied to GND (1 more pin is gone)

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that XMEGA A has some interesting issues.

But Atmel have phased out the Xmegas (eg xmega128a1) that had the faulty ADCs replacing them with "fixed" chips that also have the bonus of USB added "for free". The 128A1 is replaced by the 128A1U for example.

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I was considering XMEGA AU, I never studied XMEGA A since I was not able to program that chip due to (another one) PDI issue