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Author Topic: Analog Ref to read audio level  (Read 715 times)
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Using an Uno, I built an audio visualizer that displays peak and average levels along with the frequency spectrum.  It is working fine.
The issue, which leads to my question is this:  The audio is tied to both the MSGEQ7 (spectrum chip) and a Shifty VU shield.  The SVU rectifies the signal which is read on A2 & A3.  The EQ7 output is read on A0 & A1 using ARef = DEFAULT.  If I switch off the spectrum display (don't execute the spectrum code) I can use ARef = DEFAULT to read the SVU output (A2 & A3).  However, if the spectrum code is being executed I need to use ARef = INTERNAL because the levels are much less.  My question is why the difference?  Why is the level reduced on A2 & A3 when I'm also reading A0 & A1?

I'm attaching a block diagram that shows the connections.


* AV Block Diagram.png (14.04 KB, 1440x900 - viewed 7 times.)
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Well, its all good.  A brief explanation is in order.  This issue appeared while bread boarding the project.  At the time, I changed the ARef based on the Spectrum switch and then as the project continued, I focused on other things.  Yesterday while looking at the code, I thought "This makes no sense."  Which prompted me to make the post.  While waiting for a reply, I wrote a test sketch that I ran last night.  To my surprise I discovered the reference voltage doesn't need to change!  I suppose all the wire used on the breadboard affected the audio level and now it works fine.

Lesson learned:  Test everything, both during design and again with the finished project.  Don't make any assumptions.

Sorry about this unnecessary cry for help.
Dennis
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