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GSKrasle
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Re: UI/Information Display
GSKrasle   4/18/2014 5:07:48 PM
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Or you could simply use a 0Ω to tie them together after an input resistor/filter until you decide to implement the separate channel.

As far as displays, if you were to use R, G for R, L, then you could use the full vertical range for each like fig. d, but overlap would be yellow! Cool. I did this with LM3915's back in the day.

Or how about this: FFT to only four (2n, if you please) bins, and call them Bass (B), Low-Mid (L), High-Mid (H), Treble (T) and map them to R, B, G, and (dim) white, and display a scrolling bargraph....

Or, with the previous suggestions, B could implement an oscilloscope X vs Y of the R vs L (smoothed) amplitude, superimposed on the spectrum display, with a "tail"....

Ah, I love displays. And Excel.

 

 

Max The Magnificent
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Re: You could be better off driving the display with FPGA
Max The Magnificent   4/18/2014 4:54:36 PM
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@betajet: It might be possible to use a Cypress PSoC 5LP to do the whole job...

I'll still need my Arduino for driving my Adafruit LED strips, but like I say, there are two parts to the problem -- extracting the spectrum data from the analog input stream and then displaying the info.

So -- for this first instantiation -- I've decided to use my Arduino to display the info, but the Cypress PSoC is certainly a contended for the front end signal analysis part of the picture.

betajet
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Re: You could be better off driving the display with FPGA
betajet   4/18/2014 4:48:27 PM
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It might be possible to use a Cypress PSoC 5LP to do the whole job.  That chip has an ARM Cortex-M3, programmable analog with things like switched capacitor filters, DSP, and programmable digital logic for your LEDs and whatever else you need.


What I don't know is whether it has enough performance to do everything you need and how much learning curve you need to climb.  There are cheap dev boards available: the PSoC4 Pioneer Kit (US$25, including both a PSoC 5LP and a PSoC4 in case you need both) and the PSoC 5LP Schmartboard (US$35) which has more I/O and comes in a DIP with 0.1" spacing.

Max The Magnificent
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Re: UI/Information Display
Max The Magnificent   4/18/2014 4:08:41 PM
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@GSKrasle: Roughly, you have these dimensions available to manipulate in displaying data: X, Y, R, G, B. But your data, the output of the FFT, only has these instantaneous dimensions: f, A. How to map two variables onto five?

That's the big question -- and I think that's where the fun is really going to come in. Did you see that table display (the second video) in my BADASS Display, Part 1 blog? It starts off with f,A mapped to X,Y, with f/X also mapped to different RGB values ... but if you keep watching it switches into a completely different display more in which the colors/pixels "swirl around" to the music .... I'm still trying to wrap my brain aroudn the underlying algorithm.


Also check out the third video with the trailing/falling/fading mpst-significant pixel...

Max The Magnificent
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Re: UI/Information Display
Max The Magnificent   4/18/2014 4:02:15 PM
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@GSKrasle: ...consider some of the diagrams you have, in particular a, c, d: Like Space Invader, the colours are fixed: you might as well use single-colour LEDs or white ones behind a striped filter: the channel, the dimension, is wasted. It is degenerate. (What a cool term!)

I know ... I know ... but I was rushed for time, and it was easy to throw these together in Visio.


My plan is to play aroudn implementing lots of differet schemes and provide the ability to switch between them -- maybe at EE Live! 2015 I will do a presentation on the various design possibilities and choices, and then show all the different types of display and get the audience to rate them -- it might be interesting to see who likes what...

Max The Magnificent
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Re: UI/Information Display
Max The Magnificent   4/18/2014 3:58:46 PM
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@GSKrasle: And the typos are free!

Happy Dance!

Max The Magnificent
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Re: UI/Information Display
Max The Magnificent   4/18/2014 3:58:08 PM
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@GSKrasle: I recommend a proper analog anti-alias filter and D-A, providing for both channels of stereo (and maybe for the other 3.1); you don't have to use more than one initially, but it's easier to have and not need than the other way 'round.

After writing my blog I started to think this way -- as you say, it's better to have both channels available if I want them later -- if I decide to then start with mono, I guess the simplest way is to just add the outputs from the D/A converters and divide the result by 2.

GSKrasle
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Freelancer
Re: UI/Information Display
GSKrasle   4/18/2014 3:55:59 PM
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And the typos are free!

GSKrasle
User Rank
Freelancer
UI/Information Display
GSKrasle   4/18/2014 3:52:25 PM
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Max,

I have put a lot of thought into many projects involving the display of information. In particular, I have thought about this precise one. (You're not the only one who has built such a thing!)

But first, on Getting the Data: I recommend a proper analog anti-alias filter and D-A, providing for both channels of stereo (and maybe for the other 3.1); you don't have to use more than one initially, but it's easier to have and not need than the other way 'round. The AA filter is really not a super big deal if you can sample really really fast and then apply a multi-rate ("decimation") filter (from a library: the computation has been amazingly optimized). This allows you to reduce the data-rate to something manageable on-the-fly. Then you will probably want to use a FFT (function from the same library) to get the frequency-(phase)-amplitude-time data. Anyway, with proper AA and fs, you have all the available data and what to do with it becomes a software problem only.

But what to do with the data, how to present it? First-off consider some of the diagrams you have, in particular a, c, d: Like Space Invader, the colours are fixed: you might as well use single-colour LEDs or white ones behind a striped filter: the channel, the dimension, is wasted. It is degenerate. (What a cool term!)

Roughly, you have these dimensions available to manipulate in displaying data: X, Y, R, G, B. But your data, the output of the FFT, only has these instantaneous dimensions: f, A. How to map two variables onto five? A simple bar-graph or cartesian graph gets 2 => 2, {f,A} =>{X,Y} leaving the three colours to be usefully employed other than on/off.

How about adding a dimension? Do the FFT on both stereo channels, and now you can have f, AR, AL. Assign them to X, Y as above, but now R, G can be used to distinguish AR, AL.

Add TIME: have the display fade after a pixel has been "hit": that would allow the R, G dimensions to have more than single-bit resolution!

What about the B dimension, though? Maybe it could represent the instantaneous sum of R, G, so that signals in common would be white, with the tip of the bar's R or G hue indicating the differences.... But R+G already looks yellow.... And it would be NICE if there were some conceivable way to display pure B.... Maybe a "peak" indicator of longer persistence? A "halo" over the bars? A horizontal "peak of all" indicator (but that wastes X)?

Oh, well, I have never been able to think-up a way to use a full-colour display for information derived from stereo audio without some redundancy, some degeneracy. I guess all that is left is to add some "art" just to make it look good.

My two cents!

 

Max The Magnificent
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Re: You could be better off driving the display with FPGA
Max The Magnificent   4/18/2014 10:59:19 AM
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@B.V.Rao: Never could make out whether it is working.

LOL That sounds like a lot of my hobby projects :-)

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