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LGT8F328P MCU Board |
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128x64 LCD Display (ST7920 chip) |
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Resistor 10k ohm |
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Resistor 4.75k ohm |
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Trimmer Potentiometer, 10 kohm |
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Pushbutton |
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Soldering Iron Kit |
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arduino IDEArduino
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How to Build a Simple Audio Spectrum Analyzer with Adjustable Settings
An audio spectrum analyzer is an electronic device or software tool that measures and visually displays the frequency spectrum of an audio signal. It shows the different frequencies present in the signal and their respective amplitudes, typically on a graph with frequency on the horizontal axis and amplitude on the vertical axis. In today's video, I will present you with a very simple way to create an audio spectrum analyzer that, despite its simplicity, has many possibilities for adjusting various parameters directly via buttons, without making any changes to the code.
I got the initial idea from a project on the rcl-radio website and decided to expand the original project with more features. The device uses LGT8F328P which is compatible with Arduino Nano 3 and is significantly cheaper but also with better performance.
For support in Arduino IDE for LGT8F328P, we need to enter the given link (https://raw.githubusercontent.com/dbuezas/lgt8fx/master/package_lgt8fx_index.json) in File - Preferences - Additional Boards Manager, and then in Tools - Boards Manager we install this microcontroller.
As I mentioned earlier, the device is extremely simple to build and consists of only a few components
- LGT8F328P MCU board
- ST7920 chip LCD display with a resolution of 128X64
- and two resistors
This project is sponsored by PCBWay (https://www.pcbway.com/activity/8th-project-design-contest.html). From September 1st 2025 to 31st Januarry 2026 PCBWay organize the 8th Priject Design Contest. All interested participants can compete in three categories: Electronic Project, Mechanical Project or AIoT Project. The best projects will receive valuable prizes in cash, value cupons and developement boards. Don't miss this unique opportunity and submit your project as soon as possible. PCBWay has all the services you need to create the project at the Best price.
As for the code, it is designed in a way that allows you to easily change many more parameters. For example, The experimental Auto Gain option is very intuitive and works flawlessly, optimally adjusting the bar movements regardless of the input signal strength.
Now let me explain the functions of this spectrum analyzer. When turning on the device, three letters can be seen on the top right of the screen. They sequentially display the current MODE of each button, and are changed by pressing the corresponding button.
- Button 1 cycles through 4 display modes:
Normal: Standard bars
Peak Hold: Bars with peak indicators
Falling Dots: Dot visualization
Mirror: Symmetrical display
- Button 2 cycles through 3 speed modes:
Normal: Standard falling speed
Fast: Quick response
Slow: Slow falling with random elements
- and Button 3 cycles through 3 sensitivity modes:
Normal: Default gain
High: More sensitive (lower gain)
Low: Less sensitive (higher gain)
And finally a short conclusion. This project showcases a simple yet versatile audio spectrum analyzer built with the LGT8F328P microcontroller, offering multiple adjustable display, speed, and sensitivity modes for a customizable audio visualization experience.
#define AUTO_GAIN 0 // Auto volume adjustment (disabled for manual control)
#define VOL_THR 25 // Silence threshold (no display on matrix below this)
#define LOW_PASS 20 // Lower sensitivity threshold for noise (no jumps when no sound)
#define DEF_GAIN 80 // Default maximum threshold (ignored when GAIN_CONTROL is active)
#define FHT_N 256 // Spectrum width x2
#define LOG_OUT 1
#define PEAK_HOLD_TIME 2000 // Peak hold time in ms
// Button pins
#define BUTTON1 8
#define BUTTON2 9
#define BUTTON3 10
// Manually defined array of tones, first smooth, then steeper
byte posOffset[16] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}; // 1500 Hz
//byte posOffset[16] = {1, 2, 3, 4, 6, 8, 10, 13, 16, 20, 25, 30, 35, 40, 45, 50}; // 4000 Hz
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit))
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))
#include <Wire.h>
#include <U8glib.h> // http://rcl-radio.ru/wp-content/uploads/2023/04/U8glib.zip
#include <FHT.h> // http://forum.rcl-radio.ru/misc.php?action=pan_download&item=297&download=1
#define EN 6
#define RW 5
#define CS 4
//U8GLIB_SH1106_128X64 lcd(U8G_I2C_OPT_DEV_0|U8G_I2C_OPT_FAST); // Dev 0, Fast I2C / TWI
U8GLIB_ST7920_128X64_1X lcd(EN, RW, CS); // serial use, PSB = GND
byte gain = DEF_GAIN;
unsigned long gainTimer, times;
byte maxValue, maxValue_f;
float k = 0.1;
byte ur[16], urr[16];
// Button state variables
bool button1State = false;
bool button2State = false;
bool button3State = false;
unsigned long button1Time = 0;
unsigned long button2Time = 0;
unsigned long button3Time = 0;
// Mode variables
byte displayMode = 0; // 0=normal, 1=peak hold, 2=falling dots, 3=symmetrical
byte speedMode = 0; // 0=normal, 1=fast, 2=slow
byte sensitivityMode = 0; // 0=normal, 1=high, 2=low
byte peakHold[16]; // Peak hold values for each band
unsigned long peakTimer[16]; // Timer for peak decay
void setup() {
delay(100);
sbi(ADCSRA, ADPS2);
cbi(ADCSRA, ADPS1);
sbi(ADCSRA, ADPS0);
Serial.begin(9600);
Wire.begin();
Wire.setClock(800000L);
lcd.begin();
// lcd.setRot180();
lcd.setFont(u8g_font_profont11r);
analogReadResolution(10); // ADC 10 BIT
analogReference(INTERNAL1V024);
pinMode(A0, INPUT); // INPUT AUDIO
// Initialize button pins
pinMode(BUTTON1, INPUT_PULLUP);
pinMode(BUTTON2, INPUT_PULLUP);
pinMode(BUTTON3, INPUT_PULLUP);
// Initialize peak hold array
for(int i = 0; i < 16; i++) {
peakHold[i] = 0;
peakTimer[i] = 0;
}
}
void handleButtons() {
// Button 1 - Display Mode Cycle
if (digitalRead(BUTTON1) == LOW) {
if (millis() - button1Time > 300) { // Debounce
displayMode = (displayMode + 1) % 4; // Cycle through 4 modes
button1Time = millis();
}
}
// Button 2 - Speed Mode Cycle
if (digitalRead(BUTTON2) == LOW) {
if (millis() - button2Time > 300) {
speedMode = (speedMode + 1) % 3; // Cycle through 3 speed modes
button2Time = millis();
}
}
// Button 3 - Sensitivity Cycle
if (digitalRead(BUTTON3) == LOW) {
if (millis() - button3Time > 300) {
sensitivityMode = (sensitivityMode + 1) % 3; // Cycle through 3 sensitivity modes
button3Time = millis();
// Adjust gain based on sensitivity
switch(sensitivityMode) {
case 0: gain = DEF_GAIN; break; // Normal
case 1: gain = DEF_GAIN / 2; break; // High sensitivity
case 2: gain = DEF_GAIN * 2; break; // Low sensitivity
}
}
}
}
void updatePeakHold() {
for (int i = 0; i < 16; i++) {
int posLevel = map(fht_log_out[posOffset[i]], LOW_PASS, gain, 0, 60);
posLevel = constrain(posLevel, 0, 60);
if (posLevel > peakHold[i]) {
peakHold[i] = posLevel;
peakTimer[i] = millis();
} else if (millis() - peakTimer[i] > PEAK_HOLD_TIME) {
if (peakHold[i] > 0) peakHold[i]--;
}
}
}
void drawModeIndicators() {
// Display mode indicators at top right
lcd.setFont(u8g_font_04b_03);
// Display mode indicator (N, P, D, S)
char modeChar = 'N';
switch(displayMode) {
case 0: modeChar = 'N'; break; // Normal
case 1: modeChar = 'P'; break; // Peak
case 2: modeChar = 'D'; break; // Dot
case 3: modeChar = 'S'; break; // Symmetrical
}
// Speed mode indicator (N, F, S)
char speedChar = 'N';
switch(speedMode) {
case 0: speedChar = 'N'; break; // Normal
case 1: speedChar = 'F'; break; // Fast
case 2: speedChar = 'S'; break; // Slow
}
// Sensitivity indicator (N, H, L)
char sensChar = 'N';
switch(sensitivityMode) {
case 0: sensChar = 'N'; break; // Normal
case 1: sensChar = 'H'; break; // High
case 2: sensChar = 'L'; break; // Low
}
// Draw all three indicators at top right
lcd.drawStr(100, 5, String(modeChar).c_str());
lcd.drawStr(110, 5, String(speedChar).c_str());
lcd.drawStr(120, 5, String(sensChar).c_str());
}
void drawSpectrum() {
lcd.firstPage();
do {
for (int pos = 0; pos < 128; pos += 8) {
int band = pos / 8;
int posLevel = map(fht_log_out[posOffset[band]], LOW_PASS, gain, 0, 60);
posLevel = constrain(posLevel, 0, 60);
if(millis() - times < 2000) {
posLevel = 60; // Startup animation
}
urr[band] = posLevel;
// Apply speed mode to falling effect
int fallSpeed = 1;
switch(speedMode) {
case 0: fallSpeed = 1; break; // Normal
case 1: fallSpeed = 3; break; // Fast fall
case 2: fallSpeed = 1; if(random(2) == 0) fallSpeed = 0; break; // Slow/random
}
if(urr[band] < ur[band]) {
ur[band] = max(ur[band] - fallSpeed, 0);
} else {
ur[band] = posLevel;
}
delayMicroseconds(200);
// Draw based on display mode
switch(displayMode) {
case 0: // Normal bars
for (int v_pos = 0; v_pos < ur[band] + 4; v_pos += 4) {
lcd.drawBox(pos, 61 - v_pos, 6, 2);
}
break;
case 1: // Peak hold with bars
for (int v_pos = 0; v_pos < ur[band] + 4; v_pos += 4) {
lcd.drawBox(pos, 61 - v_pos, 6, 2);
}
// Draw peak dots
if(peakHold[band] > 0) {
lcd.drawBox(pos + 1, 61 - peakHold[band], 4, 1);
}
break;
case 2: // Falling dots
for (int v_pos = 0; v_pos < ur[band]; v_pos += 4) {
lcd.drawBox(pos + 1, 61 - v_pos, 4, 1);
}
break;
case 3: // Symmetrical mode
for (int v_pos = 0; v_pos < ur[band] + 4; v_pos += 4) {
lcd.drawBox(pos, 61 - v_pos, 6, 2);
lcd.drawBox(pos, 3 + v_pos, 6, 2); // Mirror at top
}
break;
}
}
// Draw mode indicators at top right
drawModeIndicators();
} while(lcd.nextPage());
}
void loop() {
analyzeAudio();
handleButtons();
updatePeakHold();
drawSpectrum();
if (AUTO_GAIN) {
maxValue_f = maxValue * k + maxValue_f * (1 - k);
if (millis() - gainTimer > 1500) {
if (maxValue_f > VOL_THR) gain = maxValue_f;
else gain = 100;
gainTimer = millis();
}
}
}
void analyzeAudio() {
for (int i = 0 ; i < FHT_N ; i++) {
int sample = analogRead(A0);
fht_input[i] = sample; // put real data into bins
}
fht_window(); // window the data for better frequency response
fht_reorder(); // reorder the data before doing the fht
fht_run(); // process the data in the fht
fht_mag_log(); // take the output of the fht
}
How to Build a Simple Audio Spectrum Analyzer with Adjustable Settings
Raspberry Pi 5 7 Inch Touch Screen IPS 1024x600 HD LCD HDMI-compatible Display for RPI 4B 3B+ OPI 5 AIDA64 PC Secondary Screen（Without Speaker）
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