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Return to Blog# FFT Algorithm Based Audio Spectrum Analyzer

This audio spectrum analyzer utilizes an ARM7 LPC2138 microcontroller to create an FFT algorithm while performing digital signal processing without the use of special DSP processor.

A very important part of modern electronics is the use of Digital Signal processing. It is possible to achieve good result when using fast conventional processor or microcontroller although the best was to perform digital signal processing is to use a special DSP processor.

A ZL6ARM prototype board is used to set up the project as it is equipped with all necessary peripherals such as MAX232 converter, LCD, and the LPC2138 microcontroller. The LPC2138 samples the input audio signal, with sampling frequency of 40kHz, where a built-in analog to digital converter is used. The 256-point Fast Fourier Transform (FFT) algorithm is performed after getting 256 samples of the signal. There are 256 complex numbers that comprise the result of FFT. The amplified spectrum of the signal comes from dividing the real and imaginary parts of those numbers by 128 and absolute values of them are displayed.

The spectrum is sent to the PC via RS232 interface and the spectrum is displayed using specially created Windows application.

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