hey guys my first post, i have used pics before and know very basic programming, (at school) i am looking to built an audio equalizer with 10 channels and i was hoping to have 8 leds per channel. now thats technically not possible because one pin cannot handle the on-off state of 8 leds at a time, but i wanted to have each row of leds hooked up to one pin and and ground swtitching from one cahnnel to the other at very high speed that the eye cannot tell and this will allow me to have all channels on one pic isntead of 10 pics, ive seen this being done in our elx class when we did a led display project which had 34 leds on one pic and used anouther chip to jump between rows at a very high speed, 60-100 times a sec i hope u understood this, now what i need is a program or at least a start on a program that will tell me how to make the pic differentiate from the channel/intensity of analog audio input to create an op wow thx for taking time to read this plz helop :arrow: :!:

 

What you are wanting is a simple spectrum analyser.

There's no problem multiplexing the LED's (using 18 pins), and you could use an A2D to read the analogue input.

The problem is seperating the frequencies!.

You could do it in hardware, with bandpass filters providing 10 different outputs, and switch the A2D between them in turn.

Or, you could use FFT (Fast Fourier Transform), an extremely complicted piece of maths which could do it all in software. The only problem is the power required, I don't know if a PIC could manage it, although I do seem to remember seeing something about it previously.

But FFT isn't for the faint hearted :P

 

thanks for the reply, yes thats exacly the answer i needed now i just got to figure out how to program a spectrum analyser

 

You may find this interesting http://www.piclist.com/techref/micro...t/picspect.htm.

Suprising what you can find with Google, I simply entered '+fft +pic'.

 

thank you kindly sir!

 

FFT is possible on a PIC, indeed someone won an award a couple of years back where they made a spectrum analiser hook straight upto a VDU.

http://www.circuitcellar.com/pastiss...98/article.htm

 

Using a high end PIC though.

That looks very similar to the PICList link I posted, I wonder if the same guy wrote the article?.

 

take a look at the "Five channel color organ." on this page , this guys got a mid range pic to do FFT by the looks of it

http://members.cox.net/berniekm/

hope it helps

 

I think its the guy who wrote the code the guy on piclist is prasing.

Its a very cool design he made, using a VDU rather than a TV to make it safer !

Also i still think of the high end PICs as low end micros

 

yeah I just went out and got a pic17c756 .. Im going to have a go at makin that spectrum analiser