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B.V.Rao
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Re: You could be better off driving the display with FPGA
B.V.Rao   4/18/2014 10:56:34 AM
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I had one 12ch. Never could make out whether it is working. Bad ears! It made to trash can long ago.

Max The Magnificent
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Re: You could be better off driving the display with FPGA
Max The Magnificent   4/18/2014 9:44:03 AM
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@B.V.Rao: If you could lay your hands on a old DIY audio graphic equaliser,  you may probably be able to use it for analog spectrum separation.

This is another brilliant suggestion. It struck me while I was writing this column that the control of the display and the extraction of the audio data are two completely different things -- I can happily construct the display now while pondering how to extract the audio dat ain the background. Using an old graphic equalizer to extract the data woudl certainly make my life a lot easier...

Do you happen to have an old 16-channel graphic equalizer lying around? LOL

Max The Magnificent
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Re: You could be better off driving the display with FPGA
Max The Magnificent   4/18/2014 9:41:15 AM
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@B.V.Rao: I suggest using your controller to run DSP and use FPGA to drive the LEDs.

That's actually a very interesting idea -- the reason I opted for the Arduino MCU driving the NeoPixel LEDs is that the timing on the LEDs is somewhat sensitive and the folks at Adafruit have already done all the work for me (bless their little cotton socks :-)

Max The Magnificent
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Re: Switched Capacitor filters
Max The Magnificent   4/18/2014 9:39:13 AM
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@Antedelivian: Have you thought about switched capacitor filters instead of your linear ones?

I have to say that I haven't -- but that's because (like so many things) I know more about the theory than the practice.

I'm really starting to think that digital processing is the way to go, because you can do so much more manipulation of the data.

 

B.V.Rao
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You could be better off driving the display with FPGA
B.V.Rao   4/18/2014 3:14:28 AM
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I suggest using your controller to run DSP and use FPGA to drive the LEDs.  You may not need so many outputs.  all the LED strips may be daisy chained.  Few years back I made a large (16x256) mono-color matrix with a very small FPGA.  it used to display graphic data placed in block RAM by a controller.

If you could lay your hands on a old DIY audio graphic equaliser,  you may probably be able to use it for analog spectrum separation.

antedeluvian
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Switched Capacitor filters
antedeluvian   4/17/2014 6:39:25 PM
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Max

Have you thought about switched capacitor filters instead of your linear ones. Now I have little experience in this and I fully expect to be shot down for something or other I do not know. The advantage of a switched capacitor filter is that the pass frequency/cutoff frequency is set by a clock frequency so it can be changed at a moment's notice. It may be possible (and you will need to investigate) to have one filter and clock it according to your "bins" looking at each one in turn. Processing speed would seem to play into this approach, but still..

The LMF100 from National/TI is a long established part with 2 channels, but Linear Tech and no doubt Analog Devices and others have parts and app notes.

Of course if you used a PSoC1 you could have it built into the chip.

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