ER-MIDI-CV4-02

Features

• Eurorack 6HP, 3U module
• Three card stack-up
  • Front Panel card
  • Controls card
    • 8 Jacks, 1 pot
  • Processor card
• Arduino Pro Mini
  • 16 MHz
  • 5V
• MIDI In
  • TRS Type A jack MIDI In
  • USB MIDI In if external FTDI card/cable
• (4) 0-5V Analog CV outs
  • MCP4822 12-bit D/A - SPI Interface
    • MCP4822 Datasheet
  • D/A has built in output opamps, set gain to 2X
    • Outputs may only swing 2x 2.048V or 4.096V (4 octaves)
• GATE output (0-5V)
• CLK output (0-5V)
• TRIG output
• Standard Eurorack 16 pin power header

Credits

• Adapted from HAGIWO's MIDI to CV module
  • Translate from Japanese to English using browser
  • Has 4 Analog Outputs instead of 2
  • Arduino Pro Mini instead of Arduino NANO
• Based also on SYNTH-MIDI-CTL-01

Arduino Pins

• Arduino Pro Mini

• Analog 1 - Speed Adjust POT
• A4 = SDA
• A5 = SCL
• D8 = LDAC1* to CV_1, CV2
• D9 = LDAC2* to CV_3, CV_4
• D13 = SPI CSK to both ADCs
• D11 = SPI MOSI to both ADCs
• D10 = SLAVE SELECT to both ADCs

Connection to FTDI

• Use FTDI-49MM card
• Right angle 1x6 pins
• Pinout

1. GND
2. CTSn (IN)
3. VCC
4. TX (OUT)
5. RX (IN)
6. RTSn (OUT)

• Arduino Pro Mini Serial Connector
• Marking matches FTDI cable pinouts/color codes

1. BLK
2. GND
3. VCC
4. RX
5. TX
6. GRN

Connectors

Processing Card Connectors

J1 - Eurorack Power

• 2x5 IDC connector
• Only uses +12V (and GND)
• Diode polarity protected, series resistor

J2 - CVs, GATE, CLK (to/from Controls card)

• J12 on Controls card
• Pinout

1. VCC (+5V)
2. GATE
3. CLK
4. CV4
5. CV2
6. POT
7. CV1
8. CV3
9. TRIGGER
10. GND

J3 - I2C

• Pinout

1. SCL
2. SDA
3. VCC (+5V)
4. GND

J4 - MIDI (to/from Controls card)

• J9 on Controls card
• Pinout

1. VCC (+5V)
2. MIDI Out
3. MIDI In
4. GND

J5 - MIDI into RX

• Remove to use MIDI from Controls card

J6 - MIDI OUT/THRU Select

• 1-2 = MIDI Thru
• 2-3 = MIDI out from Arduino TX

Controls Card Connectors

J1 - CLK

• MIDI Clock out
• 0-5V, Digital

J2 - CV1 Out

• Control Voltage out
• 0-5V Analog Clock

J3 - CV2 Out

• Control Voltage out
• 0-5V Analog Clock

J4 - CV3 Out

• Control Voltage out
• 0-5V Analog Clock

J5 - CV4 Out

• Control Voltage out
• 0-5V Analog Clock

J6 - TRIGGER

• MIDI Trigger out
• 0-5V, Digital

J7 - GATE

• MIDI Gate out
• 0-5V, Digital

J8 - MIDI In

• MIDI Input
• TRS Type A

J9 - MIDI Out

• MIDI Output
• TRS Type A

J10 - CVs, GATE, CLK, TRIG

J11 - MIDI

Application

• Use with ER-VCO-03 to control pitch and Mod
  • CV_1 = V/OCT
  • CV_2 = MOD
• Use GATE output into ER-ADSR-555-01 output of ADSR to MOD input of ER-VCA2-01 to control amplitude
• Arduino MIDI Library
• MIDI Notes

Download steps

• Unplug MIDI in cable from front panel
• Connect FTDI card with 1:1 cable
• Download code in Arduino IDE
• Disconnect FTDI
• Connect MIDI in cable to front panel

Card Test Code

• TestPotDigIOs - Test Digital Outputs (CLK, TRIG, GATE) and Speed Pot
• ER_MIDI_CV4_04_TEST_DACs - Read pot, scale value. write to 4 analog outputs. Also, drive CLK, TRIG, GATE digital outputs

HAGIWO code baseline

• SYNTHMIDICTL01.ino
  • Runs on Arduino ATMEGA328 (Arduino NANO or Pro Mini)
  • Used as baseline and converted to CircuitPython

Working Code

• ER_MIDI_CV4_02 - Working code

// V/OCT LSB for DAC
// ER-VCO-03 characteristics
//  PITCH ADJ knob roughly centered
//  0V = 93.08 Hz (roughly F2)
//  1V = 179 Hz (G3)
//  1.52V = 261 Hz (C4)
//  2V = 365 Hz (G4)
//  3V = 722 Hz (G5)
//  4V = 1.45 KHz (G6)
//  5V = 3.05 KHz (G7)
// Max output voltage of this card is 4.096V (4 octaves)
//  1mV per DAC count
// 12 notes per octave = 1/12V per note = 83.333 mV
// Steps are in 83.333 mV
// Table counts up by integer steps - rounded 83.333 mV

3D Views

• Controls card side view

• Processing card side view

Videos

• HAGIWO MIDI to CV module

• Midi2CV - A utility module for converting MIDI messages to CV] Benjie Jiao - DIY Modular Synth Project_

Issues

Rev 1

• Daughtercard
  • Missing connection D14 anode to GND
    • Add wire D14-Anode to D9-Anode
  • R1 is close to Arduino socket (fit OK, but tight)
    • Moved down a bit

Assembly Sheet

• ER-MIDI-CV4-02 Rev 1 Assembly Sheet