Digital 6-Channel Colour Organ

Hi guys,

This is my first post here, though I've been visiting this forum for a while. Guess I just never had anything interesting to say.

Anywho, I recently got an STM32F4 Nucleo board (It's a bit like an Arduino with more bits and Hertz...and an FPU!) and have been having some fun with the DSP library. I've managed to concoct a 6-channel colour organ by sampling a single audio channel at 20kHz and feeding it into a 512-point FFT. Each output LED represents a predefined bin of a particular frequency range, and the final value is determined by taking the maximum within that bin...pretty standard stuff.

It actually produces a very nice effect, but I'm new to audio visualization so I was hoping to open up a discussion to see if anyone had any tricks/ideas to make the effect as interesting as possible. All the colour organ designs I've seen are <= 4 channels, so I can't find much about it.

These are the frequency bins I'm using so far:

Bin 1: 1Hz -70Hz
Bin 2: 190Hz -400Hz
Bin 3: 650Hz-900Hz
Bin 4: 1000Hz 1500Hz
Bin 5: 1800Hz 2500Hz
Bin 6: 3500Hz-6000Hz

If anyone is interested I could throw up the source code I have so far. Please let me know what you think!

Fun board,
What price?
Do you have the LCD?
Are you working in C?

What I have done has a simple "LED" display. I want some history but don't have the CPU power to get it. The picture is not exactly what I want but.....The back line is the audio level this pass. The Thin line to the left is the history over several seconds that disappear going left. When I am recording, by the time I hear something the meters now do not display what happened. I would like to look back one word or one note and see what that was.

A 3D looking thing that has both the LED look for "now" and a o-scope trace for "history".

The price is surprisingly low: Only $12 from Mouser. And yeah, I'm writing in C.

The LCD display seems like a nifty idea, the STM32F4 has a DMA module so you could probably shuttle data to a small LCD over SPI without even getting the processor involved. I just wonder if one of those "microcontroller-friendly" tiny LCDs would be big enough...maybe I should nab one!

WOW that is a great price. I would expect $120 or more.
When I looked up the board yesterday there was a matching LCD.
I would love to play with this but my C-ability is low.
I have looked at boards with graphic programming. (I can move pictures around) lol

I want to make an audio limiter/compressor. I have made very complex limiters using analog parts. To go beyond I need digital.

When I learned programming we started with x86 assembly...C seemed easy after that

Embedded C can still be tricky when the optimizer eats your code.

ST provides a nifty program where you select the peripherals you want to use and it writes the necessary boilerplate code for you...saves a lot of time from hunting down the exact sequence of functions needed to get things working.

Thanks,
My goal this year is to get a beagle bone black and start on a new home automation computer.
That is a ARM computer.

I was raised in eastern Alberta.