fft spectrum analyzer on avr

first of all, the song you are hearing is not the one the analyzer processes...
it analyzes "play" by flunk from the line out of my radio...
changed due "copyright infringement" :-!

yeah yeah... dont like warner anymore ^^



my homebrew audio spectrum analyzer for atmel avr temporary running at 7mhz and 128 points (atmega8).
display is an ea dogm162 in blue with white backlight.
music is (now) 'the way i feel' by 12 stones (Wind-up Records rulez!!).

enjoy the video!!

Category:

Science & Technology

Tags:

• AVR
• FFT
• spectrum
• analyzer
• mikrocontroller
• flunk
• play
• audio
• electronic
• lcd
• atmel
• display
• atmega8
• 12
• stones
• the
• way
• feel
• equalyzer

[d3u1d4e]

How many ADC measurements go into each FFT calculation (i.e. what is your "window" length - and for that matter do you apply any window function before computing FFT), and, are all calculations done in floating-point? Finally, which AVR chip did you use?

Good work!

[Z3R0gr4vi7y]

its all in the text next to the video ;)

the avr (atmega8) takes 128 12 bit adc measurements for each computing cycle...

the window function is disabled right now, but u can use it to "amplify" the spectrum information... sorry, thats hard to explain in english ^^

[d3u1d4e]

Thanks. You have your AVR clocked at 7MHz, but what is your ADC sample rate?

[Z3R0gr4vi7y]

im not quite sure... lol... its too long ago ;)

but it must be something around 50khz

[xifyh]

7 Mhz it's too slow for this project

[Z3R0gr4vi7y]

as you can see 7 mhz is more than enough to calculate the fft ;) the fft itself uses a butterfly-algorythm which makes it much faster. also the highest frequency that occurs in the audio-signal is around 0,02 mhz, so you have enought time with 7 mhz to sample, resort and calculate the signal ^^

[cronx1337]

Do you even know what FFT is??

[fullofhate77]

Great project! I'm a noob to AVR programming, and I'm trying to put a up project that will take vibration input from an accelerometer and output an alarm sound when a certain frequency is present past a given amplitude threshold. I have an ATmega328 and AVR Studio 4. I've looked online for similar projects, but the explanations are so full of tech jargon that I have to refer to Wiki 20 times before I reach the end of a paragraph. Any advice or pointers?

[yanava]

Which ADC are you using? The internal one in the AVR hits 15ksps on 10 bits. You can't sample proper audio with that, so what are you using?

[cenoa]

Microchips dsPic family has fft module.

[EdgeVetto]

FFT is short for Fast Fourier Transform. You'll find a lot of theory and explanations on google if you look.

[xxfoobarxx]

genial