Arduino 16 Channel PWM Shield – PWM Test using ATmega328P with Proteus Simulation

Introduction

This microcontroller project demonstrates how to test and generate PWM signals using the Adafruit 16-Channel PWM/Servo Shield with an Arduino-compatible ATmega328P in a Proteus simulation environment.
The project focuses on driving all 16 PWM outputs in a smooth wave pattern, making it ideal for learning multi-channel PWM control in embedded systems.
Using the PCA9685 12-bit PWM driver, this setup offloads timing-critical PWM generation from the microcontroller.
It is a practical electronics example for understanding I2C-based peripherals, PWM resolution, and simulation-friendly firmware design.
This project is especially useful for embedded systems learners working with Arduino, Proteus simulation, and PWM-based applications.

How the Project Works (Overview)

The ATmega328P communicates with the PCA9685 PWM driver over the I2C bus using the Arduino Wire library.
The PWM driver generates independent 12-bit PWM signals on 16 output channels without consuming Arduino timers.
In this test project, the firmware continuously updates PWM duty cycles to create a phase-shifted “wave” pattern across all channels.
Each output receives a slightly delayed PWM value, producing a smooth, flowing waveform suitable for LEDs, motors, or servo testing.

Block Diagram / Workflow Explanation

1. ATmega328P (Arduino Core) initializes I2C communication

2. Wire Library handles SDA/SCL data transfer

3. Adafruit PWM Servo Driver Library configures PCA9685 registers

4. PCA9685 PWM Controller generates 12-bit PWM signals

5. 16 PWM Outputs change duty cycles in a wave pattern

This workflow allows accurate multi-channel PWM generation while keeping the firmware simple and efficient.

Key Features

• 16 independent PWM output channels

• 12-bit PWM resolution (0–4095 steps)

• I2C-based communication using SDA and SCL

• Reduced PWM frequency optimized for Proteus simulation

• Smooth wave-style PWM output across all channels

• Minimal microcontroller timer usage

Components Used

• ATmega328P microcontroller

• Adafruit 16-Channel PWM/Servo Shield

• PCA9685 16-channel 12-bit PWM driver

• I2C communication lines (SDA, SCL)

• Arduino AVR firmware environment

Applications

• Multi-LED brightness testing

• Servo motor signal verification

• PWM output diagnostics

• Embedded systems PWM learning projects

• DIY electronics involving motor or LED arrays

Explanation of Code (High-Level)

The firmware starts by initializing serial communication for debug output.
The Wire and Adafruit_PWMServoDriver libraries handle I2C communication and PWM control.
During setup, the PCA9685 is initialized and configured to operate at 100 Hz, which improves simulation stability in Proteus.
In the main loop, PWM values increment gradually and are phase-shifted across all 16 channels.
This creates a continuously moving wave effect, demonstrating precise and synchronized PWM control.

Source Code

Download

void setup() {
  Serial.begin(9600);
  Serial.println("16 channel PWM test!");

  // if you want to really speed stuff up, you can go into 'fast 400khz I2C' mode
  // some i2c devices dont like this so much so if you're sharing the bus, watch
  // out for this!

  pwm.begin();
  //pwm.setPWMFreq(1600);  // This is the maximum PWM frequency
  pwm.setPWMFreq(100);     // For simulation efficiency we reduce the maximum PWM frequency. 
  
  // save I2C bitrate
  uint8_t twbrbackup = TWBR;
  // must be changed after calling Wire.begin() (inside pwm.begin())
  TWBR = 12; // upgrade to 400KHz!

Download Source Code

Proteus Simulation

In the Proteus simulation, the ATmega328P communicates with the PCA9685 over the I2C bus.
Each PWM output shows a dynamically changing waveform, phase-shifted relative to adjacent channels.
The reduced PWM frequency ensures stable waveform visualization and smooth simulation performance.
This setup accurately represents real hardware behavior for PWM testing and validation.

(FAQs)

Conclusion

This Arduino 16-Channel PWM Shield project is a clean and effective way to understand multi-channel PWM control using Proteus simulation.
By leveraging the PCA9685 driver, complex PWM tasks are simplified while maintaining high resolution and accuracy.
It serves as a valuable embedded systems learning project for PWM control, I2C communication, and practical electronics experimentation.

Complete File

Arduino 16 Channel PWM Shield – PWM Test using ATmega328P with Proteus Simulation

Download Complete File