MOD1 - Modular Utility Collection#

MOD1 is Hagiwo’s versatile utility module collection offering 12 different firmware options for a wide range of modular synthesis tasks. From LFOs and envelopes to logic processing and VCOs, MOD1 is your Swiss Army knife for Eurorack.

Hardware: Arduino Nano · Compact Design · Triple Potentiometer Control · Multiple I/O

3-Channel LFO

3-Channel LFO module design
🔍 Click to enlarge

Features

- 3 independent LFO outputs - Selectable waveforms: Triangle, Square, Sine, Random Slope - Individual frequency control per channel - Global CV frequency input affects all channels - Frequency range: 0.02 - 5Hz - Waveform selection saved to EEPROM **Perfect for:** Multi-source modulation, complex movement, parallel LFO routing **Controls:** - **POT1**: LFO1 Frequency - **POT2**: LFO2 Frequency - **POT3**: LFO3 Frequency - **F1 Input**: Global frequency CV (affects all channels) - **Button**: Change waveform (Triangle → Square → Sine → Random Slope)

ADSR Envelope Generator

ADSR Envelope Generator module design
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Features

- Classic ADSR envelope with CV output - Attack phase gate output (gate-to-trigger conversion) - Decay-to-release phase gate output (trigger-to-gate conversion) - 6-level sustain control via button - PWM envelope output - Sustain level saved to EEPROM **Perfect for:** VCA control, filter modulation, percussion shaping **Controls:** - **POT1**: Attack Time - **POT2**: Decay Time - **POT3**: Release Time - **F1 Input**: Trigger Input - **F2 Output**: Attack phase gate - **F3 Output**: Decay-to-release phase gate - **F4 Output**: ADSR envelope CV - **Button**: Cycle through 6 sustain levels

Chipz

Chipz module design
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Features

- 2 independent pwm outputs - Clock input and internal Clock fallback - Can be used with headphones **Perfect for:** First encounter with the MOD1 module **Controls:** - **POT1**: - **POT2**: - **POT3**: - **F1 Input**: Clock input - **Button**: Toggle mode / song

Clock Divider/Multiplier

Clock Divider/Multiplier module design
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Features

- 3 independent clock outputs - Division/multiplication rates: 1, 2, 3, 4, 8, 16 - Mode switching: Divider ↔ Multiplier - Pin change interrupts for zero-latency edge detection - Direct port manipulation for fastest I/O - Mode stored in EEPROM **Perfect for:** Polyrhythms, tempo variations, synchronized modulation **Controls:** - **POT1**: Output 1 rate (1, 2, 3, 4, 8, 16) - **POT2**: Output 2 rate - **POT3**: Output 3 rate - **F1 Input**: Clock input - **Button**: Toggle Divider/Multiplier mode

Envelope Generator (AR)

Envelope Generator (AR) module design
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Features

- Attack-Release envelope generator - 3 outputs: EG, Inverted EG, End-of-cycle pulse - Self-patchable for LFO or clock functionality - Output level control - Exponential curves via lookup table **Perfect for:** Percussion, fast envelopes, gate-to-trigger conversion **Controls:** - **POT1**: Attack Time - **POT2**: Release Time - **POT3**: Output Level - **F1 Input**: Trigger Input - **F2 Output**: End-of-cycle pulse - **F3 Output**: Inverted EG output - **F4 Output**: EG output - **Button**: Manual trigger

Euclidean Rhythm Sequencer

Euclidean Rhythm Sequencer module design
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Features

- 8 or 16-step Euclidean rhythm generator - Adjustable number of hits (0-8) - Output probability control (randomize triggers) - Step length: 8 steps ↔ 16 steps - CV control for number of hits - Reset input **Perfect for:** Generative rhythms, polyrhythmic patterns, controlled randomness **Controls:** - **POT1**: Number of hits (0-8) - **POT2**: Output probability - **POT3**: Step length (8 or 16 steps) - **F1 Input**: Reset - **F2 Input**: Clock - **F3 Input**: Number of hits CV - **F4 Output**: Trigger output - **Button**: Manual reset

LFO (Single Channel)

LFO (Single Channel) module design
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Features

- 5 waveforms: Sine, Triangle, Sawtooth, Square, Random Slope - Continuous waveform selection via pot - Frequency CV input - Waveform CV input - Output level CV input - Switchable frequency range (saved to EEPROM) **Perfect for:** Classic modulation, CV mixing, voltage-controlled waveshaping **Controls:** - **POT1**: Frequency - **POT2**: Waveform selection - **POT3**: Output level - **F1 Input**: Frequency CV - **F2 Input**: Waveform CV - **F3 Input**: Output level CV - **F4 Output**: LFO output - **Button**: Change frequency range

Logic Processor#

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Features

  • 6 logic modes: AND/NAND, OR/NOR, XOR/XNOR, COMPARE, MAX/MIN, FLIP-FLOP
  • Dual PWM outputs (A and B)
  • Two CV inputs with pot control
  • Real-time logic processing

Perfect for: Complex CV processing, gate logic, voltage comparisons

Controls:

  • POT1: Mode select
  • POT2: Input A value
  • POT3: Input B value
  • F1 Input: CV Input A
  • F2 Input: CV Input B
  • F3 Output: PWM Output A
  • F4 Output: PWM Output B

Random CV Sequencer

Random CV Sequencer module design
🔍 Click to enlarge

Features

- Quantized random CV output (C2-C5 range) - Step lengths: 3, 4, 5, 8, 16, 32 - Output level sets top note (0-36 semitones) - Trigger probability control - Scale selection via button (multiple scales) - Serial tuning menu (hold button at boot) - Calibration table stored in EEPROM **Perfect for:** Generative melodies, random sequences, quantized randomness **Controls:** - **POT1**: Step length - **POT2**: Output level (top note) - **POT3**: Trigger probability - **F1 Input**: Clock input - **F2 Input**: Re-randomize trigger - **F3 Output**: CV output (quantized) - **F4 Output**: Trigger output - **Button**: Re-randomize / Scale select (long press)

Rose Oscillator

Rose Oscillator module design
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Features

* Rose curves are generated by plotting r = sin(k*theta) in polar coordinates * where k is the harmonic ratio (multiplier/divisor) * * This creates complex waveforms with multiple "petals" that sound like * harmonic-rich oscillators with unique timbres **Perfect for:** complex sounding oscillatoors or just fancy Laser patterns :) **Controls:** - **POT1**: Harmonics morphing (rose shape) - **POT2**: Harmonic ratio (k parameter) - **POT3**: Coarse frequency/tuning - **F1 Input**: CV Input / V/Oct pitch CV - **F2 Output**: X - Left component of complex signal - **F3 Output**: Y - Right component of complex signal - **F4 Input**: Trigger input (CV options) - **Button**: change modes / change CV mapping

3D Knot Oscillator

3D Knot Oscillator module design
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Features

* Three beautiful knot patterns: * 0. Trefoil Knot * 1. Lissajous Curve * 2. Torus Knot * * View on oscilloscope in X-Y mode! **Perfect for:** complex sounding oscillatoors or just fancy Laser patterns :) **Controls:** - **POT1**: Knot selection - **POT2**: Waveform variation - **POT3**: Frequency - **F1 Input**: Knot morph - **F2 Output**: X - Left component of complex signal - **F3 Output**: Y - Right component of complex signal - **Button**: change modes

Square Wave VCO

Square Wave VCO module design
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Features

- V/Oct tracking square wave oscillator - Octave control with CV input - Vibrato LFO with depth control - Chiptune-style octave LFO (toggle on/off) - Audio-rate output **Perfect for:** Audio oscillator, chiptune sounds, square wave bass **Controls:** - **POT1**: Frequency tune - **POT2**: Octave - **POT3**: Vibrato LFO level - **F1 Input**: V/Oct CV input - **F2 Input**: Octave CV input - **F3 Input**: Vibrato level CV input - **F4 Output**: Audio output - **Button**: Octave LFO on/off **Note:** Remove capacitor from D11 output circuit for proper audio operation

Sync LFO

Sync LFO module design
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Features

- Clock-synchronized LFO - 5 waveforms: Sine, Triangle, Sawtooth, Square, Random - Division rate control - Waveform selection via pot or CV - Output level control - External clock input via button or F1 **Perfect for:** Tempo-synced modulation, rhythmic LFO, clocked movement **Controls:** - **POT1**: Division rate - **POT2**: Waveform selection - **POT3**: Output level - **F1 Input**: External clock (when button pressed) - **F2 Input**: Division rate CV - **F3 Input**: Waveform select CV - **F4 Output**: LFO output - **Button**: Use external clock

Tap Tempo Clock#

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Features

  • 4-output tap tempo master clock
  • F1: Fixed 4x output
  • F2: 1-16x variable multiplication
  • F3 & F4: 1/1 to 1/16 variable division
  • Tap tempo via button (4 taps to set)
  • BPM range up to ~280 BPM

Perfect for: Master clock, tempo setting, synchronized rhythms

Controls:

  • POT1: F2 output multiplication rate (1-16x)
  • POT2: F3 output division rate (1/1 - 1/16)
  • POT3: F4 output division rate (1/1 - 1/16)
  • F1 Output: 4x clock output
  • F2 Output: Variable multiply output
  • F3 Output: Variable division output
  • F4 Output: Variable division output
  • Button: Tap tempo (tap 4 times)

Trigger Burst

Trigger Burst module design
🔍 Click to enlarge

Features

- Clock-syncable trigger burst generator - Burst counts: 1, 3, 4, 6, 8, 16 - Burst frequency divisions: /2, /3, /4, /6, /8, /16 - Internal clock (~280 BPM max) or external clock - CV control for burst number - Manual or trigger input activation **Perfect for:** Trigger multiplication, rhythmic bursts, drum fills **Controls:** - **POT1**: Burst number (1, 3, 4, 6, 8, 16) - **POT2**: Burst frequency (division of master clock) - **POT3**: Internal clock rate (or external when fully left) - **F1 Input**: External clock input - **F2 Input**: Trigger input - **F3 Input**: Burst number CV - **F4 Output**: Trigger burst output - **Button**: Manual trigger

Hardware Requirements#

  • Arduino Nano or Arduino Nano (Old Bootloader)
  • MOD1 Hardware (available from various Eurorack DIY sources)
  • 3 Potentiometers for parameter control
  • Push Button for mode selection/triggering
  • LED for visual feedback
  • Multiple I/O Jacks (4 jacks: F1-F4)

Installation Instructions#

1. Connect Your Module#

  • Connect your Arduino Nano to your computer via USB
  • Ensure the module is powered

2. Select Firmware#

  • Choose the firmware that matches your needs from the options above
  • Click the appropriate button (Nano or Old Bootloader)

3. Flash Firmware#

  • Your browser will prompt you to select the serial port
  • Select the port corresponding to your Arduino
  • Wait for the upload to complete (typically 10-30 seconds)

4. Verify#

  • The module should boot up with the new firmware
  • Test the inputs/outputs to confirm proper operation
  • Check LED feedback for visual confirmation

About MOD1#

MOD1 is Hagiwo’s collection of utility modules designed for maximum flexibility in a compact Eurorack format. Each firmware transforms the same hardware into a completely different tool, making MOD1 one of the most versatile modules in your rack.

Key features across all firmware:

  • Easy to Build: Minimal component count
  • Flexible: 12 different firmware options
  • Reprogrammable: Change firmware as your needs evolve
  • Educational: Great for learning Arduino and Eurorack DIY

The compact design and triple-pot interface provide hands-on control while keeping your rack tidy.

Troubleshooting#

Upload fails:

  • Ensure you’re using Chrome, Edge, or Opera (Web Serial API required)
  • Try unplugging and reconnecting the USB cable
  • Check that no other software (Arduino IDE, serial monitor) is using the port

Module doesn’t respond:

  • Check power connections
  • Verify correct board selection (Nano vs Old Bootloader)
  • Try the opposite bootloader version

Outputs not working:

  • Check your power supply
  • Verify the firmware uploaded successfully
  • Test with a multimeter to check for voltage output
  • Confirm proper wiring of output jacks

Button not responding:

  • Some firmware use button for mode selection, others for triggering
  • Check if button requires pull-up resistor
  • Verify button wiring

Resources#

Based on Hagiwo’s designs · Enhanced by the Modulove community