ReadMe First!!

This module is made of two PCBs: a main board and a front board. Both are in the need to realize this module!!

PCBWay shared projects form allows for only one gerber to be uploaded. Check this article attachments under "Schematic and Layout" for the front board gerber files and order it too.

Introduction

Waveshape monitors have been more and more common in commercial synthesizers. These can be placed at the end of the audio path to visualize the effect on the whole chain (think in example to Korg and their "-logue" series of synthesizers) but also as pure oscillator wave monitors (Moog One has three, one per oscillator!).

Whether you are really convinced that this type of utility can be useful in sculpturing the best sound ever or not, the charm of this novelty object is undeniable and having the possibility to add such toy to your rig will likely be a welcome news.

I really wanted one for my DIY modular synth, so ended designing an eurorack-ready module with only few components and some line of code. Nice uh :)

What a Waveshape Monitor Is (and What It Is Not)

A waveshape monitor is essentially a "limted" oscilloscope, with no measurement capability. It's funtion it to give the user a representation of the shape of an incoming wave, being it a signal from an oscillator or a periodic modulation source.

On the plus side, the ease of use. You don't have to worry about trigger levels, X and Y axis scales and so on: incoming signals are displayed at any time, with their amplitude always maxed out to the whole screen area

It is not used to debug circuits: it's meant to be a "musical" device, to help musicians sculpture their sound.

The Circuit

This project is built around an op-amp in differential amplifier configuration. This is because in eurorack world we can expect voltages from -12V to +12V hitting the input of our microcontroller board, which is not tolerant to such a voltage extension. With a differential amplifier we "compress" such voltage range into a more microcontroller-friendly "zero-to-5" volt range.

The microcontroller board (Arduino Nano with ATmega 328p microcontroller) is also in charge to visualize onto the 0.96" OLED display the waveform. As said, the waveform is always maxed out to fill the whole screen in order to be more readable by the musician.

Please notice that resistors values are tuned for a +/-12V signal max. If your sistem is expected to send signals in the +/-15V range, resistor values should be changed accordingly. In particular, the two 4.7K ohm resistors should be replaced with at least 5.6K ohm resistors.

The Module

The module is made up of two FR4 boards: main and front board. Both have circuits printed on them, so you are in the need for both to have the module working.

DO NOT USE ALUMINUM FOR THE FRONT BOARD! Both PCBs must be FR4. It is not possible to use aluminum PCB because of the need for some through-hole electrical connection between the main board, the panel board and the OLED display.

To make assembly easier and faster, component values are silkscreened on boards: no annoying components maps are needed ;)

The main PCB board is intended to be mounted parallel to the front board.

An important note about the OLED display: the same ID (SSD1306) is used for different OLED displays out there. There could be slight size differences (nothing to worry about), number of pins, but also pinout differences.

When you order your display take care to get one with four pins, not seven. Among four pins displays, you can find pinout differencies, as said. This module adopts those with GND on the far left, by looking at the display area. There are versions with Vcc (+5V) at the far left instead. These latest are not compatible with the front panel PCB attached to this article and will likely burn and/or cause severe damage to the display if used (in the two different versions GND and VCC are swapped).

Have fun with your build!!