REMI Synth 'Lite' variant
Monophonic MIDI Sound Synthesizer based on PIC32MX MCU

A DIY Project by M.J. Bauer

remi synth lite

The REMI Synth 'LITE' is battery-powered with OLED display and headphone amp.

Designed especially as a companion sound module for the REMI 2 handset (MIDI wind controller), this 'Lite' version of the REMI Synth is a more compact battery-powered device using the same "sound engine" software as the other REMI synth models (also based on a PIC32MX MCU). The 'Lite' synth can be attached to the player's belt or pocket with Velcro or a metal clip, allowing more freedom of movement while playing through headphones. A wireless audio transmitter (as used on electric guitars) may be plugged in for cable-free performance with an instrument amplifier.

The front-panel user-interface (GUI) is simplified, providing only a few essential day-to-day operations. The GUI comprises a tiny (1.3 inch) OLED display and 2 push-buttons.

The back panel provides a MIDI IN socket (DIN-5) with "power-over-MIDI" (5V DC output) to support a REMI 2 handset or any other MIDI controller with a classic MIDI OUT connection. There is a headphone socket (3.5mm TRS jack) and a low-level output (1/4-inch phone jack) for connection to an instrument amplifier.

A USB port provides the same command-line user interface (CLI) as the other REMI Synth models. The USB connection can supply 5V DC power to the synth module. It also powers the built-in battery charger.

front view

back panel


The circuit board is built around a PIC32MX340 "audio dongle" designed by a project follower "Chua" who lives in Singapore. Chua's PCB has provision for the I2C EEPROM (24LC08) and PWM audio output components, but access to MCU I/O pins is very limited, so the PCB must be "hacked" to get enough I/O for the synth. 

For example, a pair of test-point pads (RC13, RC14) are used for the two push-button inputs. The I2C bus signals (SCL, SDA) required for the OLED display are accessed from the EEPROM (pins 5 & 6). The 6-pin ICSP header provides a further two port pins (RB6, RB7) which are used in the battery charging circuit.

Chua dongle PCB

The complete circuit board assembly is shown here..

top side annotated

topside view

underside wiring


View/download REMI synth 'Lite' schematic diagram

The enclosure is a plastic box, size 130 x 65 x 42 mm. This photo shows the internal layout...

internal layout

A few of the GUI screens...

GUI presetGUI batt
GUI reverb<Vibrato settings>


... to be continued ...

<to do: Add notes on battery-charger operation.>

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Last update: Sept-2023

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