Simulates a Hammond organ and Leslie speaker on different Arduino models and other boards.

First you must install support for this MCU in Arduino IDE:

Arduino NANO/UNO/MEGA: It is supported by default

ESP8266: https://www.google.com/search?q=esp8266+on+arduino+ide

ESP32: https://www.google.com/search?q=esp32+on+arduino+ide

Once support for your board is installed, you must install this library from the Arduino library manager; Just search for 'electuno' and the available versions will appear. Inside Arduino IDE, go to the menu 'file->examples->electuno->your_board'

Simulating the Sound of Hammond Organ and Leslie Speaker with Microcontroller Power: A Deep Dive into the Electuno Project

In the world of electronic musical instruments, no sound is as unique and powerful as the Hammond Organ working in conjunction with a rotating Leslie Speaker. The Electuno project miniaturizes Digital Signal Processing (DSP) algorithms into small microcontroller boards, ranging from 8-bit Arduino families to high-performance ESP32s, to digitally recreate the legendary organ sound.

Supported Hardware and Setup

The core of Electuno is its highly flexible code design (Hardware Abstraction), allowing it to run on various architectures as follows:

1. Arduino NANO/UNO/MEGA: Despite limited resources (ATmega328P/2560), the system can remarkably simulate analog audio signals using high-frequency Pulse Width Modulation (PWM) techniques.
2. ESP8266: This cost-effective Wi-Fi board boasts a higher clock speed than typical Arduinos, enabling more complex calculation of Drawbar Sine Waves.
3. ESP32: With its Dual-core 32-bit architecture featuring an integrated DAC (Digital-to-Analog Converter) or the ability to connect via I2S for Hi-Fi audio quality, this project will unleash the ESP32's maximum performance for both Polyphony and Leslie effects.

Environment Setup

Before you begin the code flashing process, you need to install the Board Support Package in the Arduino IDE for your chosen board:

• ESP8266: Find installation instructions via Google: esp8266 on arduino ide
• ESP32: Find installation instructions via Google: esp32 on arduino ide

Once your board is ready, go to the Library Manager in the Arduino IDE and search for 'electuno' to install the latest Library version, which includes all necessary Header files and example code.

Deep Dive into Synthesis Logic

Simulating a Hammond Organ is not merely playing Sampling audio files; it utilizes Additive Synthesis, similar to the Tonewheels mechanism in the real instrument.

1. Drawbar and Tonewheel Simulation

A Hammond Organ features nine sliders (Drawbars), each controlling the level of a different Harmonic. In Electuno's code, multiple Sine wave Oscillators are generated simultaneously. The signal strength values from each Drawbar are then mixed together in the main operational Loop to create complex audio waveforms.

2. Leslie Speaker Algorithm (The Rotary Effect)

The hallmark of a Leslie Speaker is its dimensional sound from the rotating speakers, which Electuno simulates through:

• Doppler Effect (Frequency Modulation): Slight frequency shifts according to the rotation rhythm.
• Tremolo (Amplitude Modulation): Changes in audio loudness as the speakers rotate towards and away from the listener.
• Crossover Filter: Separating low-frequency (Woofer) and high-frequency (Horn) audio bands to simulate the different rotation speeds of the two components.

Code Structure and Usage

You can access example code tailored for each board by navigating to File -> Examples -> electuno -> [your_board].

Basic Logic Analysis in the Example:

// Conceptual Logic Example
void loop() {
  // Read values from MIDI or buttons
  uint8_t note = getMidiNote();
  
  // Calculate signals from all 9 Drawbar sets
  float sample = 0;
  for(int i=0; i<9; i++) {
    sample += oscillators[i].nextSample() * drawbarGains[i];
  }
  
  // Apply Leslie effect (Rotary Speaker)
  sample = applyLeslieEffect(sample, rotationSpeed);
  
  // Output to Output (PWM or DAC)
  outputAudio(sample);
}

In a real Electuno system, an Interrupt Service Routine (ISR) or I2S DMA Buffer is used to ensure continuous audio signal output without Jitter, even when the CPU is processing other instructions.

Demo Videos

To visualize the operation and audio quality achieved by these small microcontrollers, you can watch the demo videos here:

The Electuno project is not just a musical instrument; it's an excellent lesson in Real-time Digital Signal Processing (DSP) on Embedded Systems for engineers and developers interested in Audio Engineering.