Objective

This course will show you how to use Microduino to get sound signal and display audio spectrum via FFT(Fast Fourier Transform) on your TV.

Equipment

Hardware needed	Number	Function
n3904 NPN triode	One	Used as an amplifier
1KΩ resistor	One	Current limit
330Ω resistor	One	Current limit
10KΩ resistor	Two	Current limit
100KΩ resistor	Onr	Current limit
2N3904 triode	One	Current limit
0.1uf capacitance	Two	Pass high frequency and stop low frequency
Breadboard	One	All components gather here
Breadboard jumper	Several	Connector
Electret microphone	One	Receive sound signal
AV interface displayer	One	Display spectrum
RCA wire	One	Video transmission line

Step 1：

First, we need an electret microphone to build a device that can receive sound signal, as follows:

Connect the output terminal to Microduino’s A0 port, you can use A0 output value to judge the circuit buildup.

Step 2：

Make RCA line, connect it to Microduino. For details, please refer to Microduino video output tutorial:

Here is the well-built circuit:

Step 3： Download the code and run. Program functions in:

1. Read data off A0 port.

2. Cut data for some time and process it with FFT.

3. Display the well-processed data in the way of scetches and lines.

4. That cycle repeats

It is displayed as follows:

You’ll see audio spectrum on displayer.