ER-VCO-03

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Tindie-mediums.png

ER-VCO-03 SET P1080788-720px.jpg

Features

  • Build of Pico VCO by HAGIWO
    • Prototyped on SYNTH-VCO-01 - Synth Voltage Controlled Oscillator
  • Digital Voltage Controlled Oscillator (VCO)
  • Eurorack 3U tall, 6HP wide (30 mm)
  • (3) Card set
  • XIAO RP2040 CPU
  • Three modes: Wavefold, FM and AM
  • PWM output with 2 pole low pass filter
  • Each mode has eight built-in waveforms
  • AC coupled output
  • (3) Switches
    • 3-position Octave Up/Down toggle
    • 3-position Mode Up/Down toggle (Wavefold, FM and AM)
    • Timbre Pushbutton switches between 8 waveforms
  • (2) Knobs
    • Freq fine adjust (sub octave range)
    • Mod adjust
  • Standard EuroRack 16 pin power header
    • Uses 5V from Eurorack power
  • Views (left to right)
    • Front Panel
    • Control Panel controls side
    • Control Panel rear side
    • Logic card rear side
    • Logic card component side (faces rear of card set)

ER-VCO CTL-03-CARD SET-3D-720PX.png

XIAO RP2040 Pins

  • Pin 1, GP26 = Vol/Oct, Analog In
  • Pin 2, GP27 = Freq Pot, Analog In
  • Pin 3, GP28 = Mod, Analog In
  • Pin 4, GP29 = Mod Pot, Analog In
  • Pin 5, GP6 = Timbre Pushbutton, select waveform type, Digital Input
  • Pin 6, GP7 = Gate (optional), Digital Input
  • Pin 8, GP1 = Octave Down, Digital Input
  • Pin 9, GP2 = Audio Output, PWM out
  • Pin 10, GP4 = Mode Down, Digital Input
  • Pin 11, GP3 = Mode Up, Digital Input
  • Pin 12 = +3.3V
  • Pin 13 = GND
  • Pin 14 = +5V

Cards

  • Three card set
    • Front Panel
    • Controls
    • Processor

Front Panel Card

ER-VCO PANEL-03 REV3 REAR 3D-720pxV.png

  • 3U tall, 6 HP wide
    • 128.4mmx30mm
  • Holes for 2 Pots, 4 Jacks, 1 Pushbutton, 2 Toggles
  • Could use for other designs
  • Re-label with White-on-Black P-Touch labels

Controls Card

ER-VCO CTL-03-REV2 FRONT REAR-3D-720pxV.png

  • 28mmx100mm
  • Pots, Jacks, Pushbutton fit through Front Panel
  • Lower right Jack - Output line
  • (3) Digital Input jacks
    • Scale resistors reduce 5V signals to 3V
    • Clamping diodes protect inputs
    • Filter cap for noise reduction
  • (2) Pots are analog inputs to Processor card
    • Filtered inputs to make pots "cleaner"
  • Headers for External Toggles
  • 2x8 and 1x3 Female Header Sockets connect to Processor Card
    • 2x8 Header Pinout
  1. Vcc
  2. Vcc
  3. N/C
  4. Oct Down Toggle (external)
  5. Mod Pot
  6. Oct Up toggle (external)
  7. Gate input
  8. Mode Up Toggle (external)
  9. Frequency adjust Pot
  10. Mode Down Toggle (external)
  11. Volts per Octave CV Analog input
  12. Modulation CV input
  13. Audio Out
  14. Timbre Pushbutton
  15. GND
  16. GND
  • 1x3 Header Pinout
  1. GND
  2. GND
  3. GND

Processor Card

ER-VCO DB-03 REV2 FRONT REAR 3D-720pxV.png

  • 28mmx100mm
  • XIAO RP2040 CPU
  • PWM output with 2-pole filter
  • Audio Amp/Driver
  • Eurorack 16 pin header
    • Uses +5V
  • 2x8 Male and 1x3 headers connect to Controls card
    • 2x8 Male Pinout
  1. Vcc
  2. Vcc
  3. N/C
  4. Oct Down Toggle (external)
  5. Mod Pot
  6. Oct Up toggle (external)
  7. Gate input
  8. Mode Up Toggle (external)
  9. Frequency adjust Pot
  10. Mode Down Toggle (external)
  11. Volts per Octave CV Analog input
  12. Modulation CV input
  13. Audio Out
  14. Timbre Pushbutton
  15. GND
  16. GND
  • 1x3 Make Pinout
  1. GND
  2. GND
  3. GND

Schematic

ER-VCO-03 REV 1 Schematic

Software

  • SYNTHVCO03.ino
    • Commented out lines that invert analog inputs for pots (1023-value) to match Rev 1 PCB

Issues

Rev 3

  • Controls card
    • No functional changes
    • SW2, SW4 mount to controls side (silkscreen only change)
    • Re-sequenced reference designators

Rev 2

  • Tested/works very well
    • C1 cap near 2x8 female 2x8 socket is close
    • Need to make sure the if side of the 2x8 comes from cutting down a header that it's trimmed tightly
      • Could install cap after the header
  • Daughtercard (CPU)
    • Change width to 28mm wide
    • Change height to 100mm
    • Move U3 ref des Silkscreen
    • Rotate CPU - USB pointing removes slot intrusion
    • Enough room to route USB connection
      • No more USB jack collision with Eurorack power jack
    • Add Rev 2 marking to Silkscreen
    • Change to 5V Eurorack operation
    • Diode switch USB and Eurorack power
    • Won't power 5V op amps with USB alone
  • Controls card
    • Change width to 28mm wide
    • Change height to 100mm
    • Rotated pots 90 deg so half-way mark is pointing up
    • Some tracks/layers improvements
    • Improved 5V pour - adjusted down to CPU
    • Flipped 5V/GND on adjustment pots so up/down don't need software adjustment

Rev 1

  • Working
    • MODE pushbutton works
    • MOD CV works
    • FREQ 1V/oct CV works
  • Front Panel card
    • WAVE-FORM Pushbutton hole is too small - drilled bigger hole
    • OCTAVE UP/DOWN, MOD UP/DOWN switches holes are too small - drilled bigger holes
  • Controls card
    • MOD and FREQ pots are backwards - easily fixed in software
  • Control/Daughtercards seem aligned to eac other OK, but skewed to Front Panel
    • Make card 28mm?
  • RP2040 hangs over USB side too far (card is wider)
    • Maybe rotate 90 degrees?
  • Put 2 toggle switches onto PCB

Assembly Sheet

Older Revs

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