midi→cv¶

reset button
digital IO (Do not connect microrack signals!)
digital IO (Do not connect microrack signals!)
modular level (from -5 to +5 V) inputs (pins 36, 37)
midi TRS input (type-A)
microrack level (from -5 to +5 V) outputs (pins 26, 25, 33)
128×64 OLED monochrome display
gate output (0 to +3.3 V, pin 12)
gate output (0 to +3.3 V, pin 13)
MIDI output (3.3 V and pin 17 out, 200 Ohm resistors included)
digital IO (Do not connect microrack signals!)
encoder + push button (enc. pins 34, 35, button pin 39)
push button (pin 38)
USB type-C for firmware update and serial connection (on bottom side)

Description¶

ESP32-D0 based programmable module with 4 MB flash, MIDI input, analog I/O, and user interface.

Use our Web Firmware Flasher to update the firmware (works only in chrome-based browsers).

Analog inputs (pins 36, 37)¶

Level-shifted inputs that convert -5V to +5V signals to 0–3.3V range suitable for the ESP32 ADC.

Analog outputs (pins 26, 25, 33)¶

All three outputs support PWM. Pins 26 and 25 also have 8-bit DAC. Each output has a first-order lowpass filter (1 kHz cutoff) and level shifting to convert 0–3.3V back to -5V to +5V range.

Gate outputs (pins 12, 13)¶

Direct microcontroller outputs for gate/trigger signals. These pins should only be connected to input pins of other modules.

Digital I/O¶

Some ESP32 pins are directly exposed without any protection circuitry. Only 0–3.3V signals are safe — do not connect these to other microrack modules!

MIDI¶

MIDI input: TRS type-A jack with optocoupler isolation, connected to pin 16
MIDI output: Pin 17 and 3.3V power exposed with 200Ω series resistors for connecting an external MIDI jack

User interface¶

OLED display: 128×64 monochrome HS96L03W2C03, I2C on pins 21 and 22
Rotary encoder: Quadrature encoder on pins 34, 35 (active low with pull-up); push button on pin 39 (active low with pull-up)
Button: Separate push button on pin 38 (active low with pull-up)
Reset button: Hardware reset
LEDs: Chain of 4 addressable SK6805-EC20 LEDs on pin 23 (2 on bottom side, 2 under the display)

USB and programming¶

CP2102 USB-UART converter connected to the main ESP32 UART. DTR/RTS lines are wired for automatic bootloader mode entry via esptool/Arduino IDE. Use for firmware updates and serial communication.

Firmware¶

Firmware source code and releases are available in the MOD-ESP32-FW repository.

You can flash the firmware using PlatformIO or use the online flasher (works only in chrome-based browsers).