ESP32 Generate a PWM wave visualizing the waveform on an OLED display

Steps:
1. Read sound sensor values from an analog pin (GPIO 4 in my case).
2. Map sound sensor input to a PWM duty cycle.
3. Generate a PWM signal using the ESP32 LEDC library.
4. Display the waveform on an OLED (SSD1306) display in real time.
Connections
• Sound sensor:
o ADC (Analog to digital converter) GPIO 4
o VCC 3.3V
o GND GND
• OLED Display:
o VCC 5.v
o SDA GPIO 7
o SCL GPIO 6
• PWM Output:
o PWM Pin Any GPIO that supports PWM (e.g.,in this case GPIO 5)

How the Code Works
This code takes input from a sound sensor, generates a PWM signal, and visualizes it as a scrolling waveform on an OLED display. Here’s how it works:
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Reading the Sound Sensor Input
• The analogRead(SOUND_SENSOR_PIN) function reads the sound level.
• The value ranges from 0 to 4095 (since ESP32 uses a 12-bit ADC).
• We map this value to a PWM duty cycle between 0 and 255:
int pwmDuty = map(soundValue, 0, 4095, 0, 255);
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Generating the PWM Signal
• ESP32 uses the LEDC API (Low-Energy LED PWM Controller) for PWM output.
• The PWM is generated on GPIO 5 using:
ledc_set_duty(LEDC_LOW_SPEED_MODE, PWM_CHANNEL, pwmDuty);
ledc_update_duty(LEDC_LOW_SPEED_MODE, PWM_CHANNEL);
• This converts sound intensity into a PWM signal, which can drive an LED, speaker, or other devices.
________________________________________
Storing and Shifting Past Sound Values
• To create a smooth scrolling waveform, we store past sound values in an array called waveform[]:
#define WAVEFORM_WIDTH SCREEN_WIDTH // 128 points for OLED width
int waveform[WAVEFORM_WIDTH] = {0}; // Buffer storing past values
• Every loop, we shift all values left and insert the new sound value at the end:
for (int i = 0; i WAVEFORM_WIDTH - 1; i++) {
waveform[i] = waveform[i + 1];
}
waveform[WAVEFORM_WIDTH - 1] = map(pwmDuty, 0, 255, SCREEN_HEIGHT, 0);
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4️Drawing the Scrolling Waveform on OLED
• We clear the display to refresh the frame:
display.clearDisplay();
• We draw the PWM value in text:
display.setCursor(0, 0);
display.print("PWM: ");
display.print(pwmDuty);
• We then connect the waveform points using drawLine():
for (int i = 1; i WAVEFORM_WIDTH; i++) {
display.drawLine(i - 1, waveform[i - 1], i, waveform[i], SSD1306_WHITE);
}
• Finally, we update the OLED screen:
display.display();
________________________________________
Adding a Small Delay
• To make the waveform scroll smoothly, we add a 50ms delay:
delay(50);
• This ensures smooth movement while keeping it responsive.

Code:
https://github.com/ukkokalevala/Pulse_Wave_Mudulation_V1.git

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