Nano Audio Experimenter Sheild PCB

This takes the Arduino Nano Mozzi Experimenter Shield PCB and swaps out three of the pots for the optional use of the following:

MCP4725 DAC.
SSD1306 display.
IO links for an analog multiplexer.

This is in addition to the remaining three potentiometers, the MIDI interface and the audio filter output.

Warning! I strongly recommend using old or second hand equipment for your experiments. I am not responsible for any damage to expensive instruments!

The Build Guide is available here: Nano Audio Experimenter Sheild PCB Build Guide.

If you are new to Arduino, see the Getting Started pages.

The Circuit

The board includes a 5V MIDI IN and unbuffered MIDI OUT. It includes a barrel jack for power directly into the Arduino Nano’s raw input.

It includes pin headers for an SSD1306 display and MCP4725 DAC and headers to allow connection to an analog multiplexer such as a 4051 (8-way) or 4067 (16 way). This is connected to A3.

There is also an audio output filter stage that can be switched between D3 or D9 for PWM output or the DAC.

The following Arduino pins are used in total:

A0, A1, A2: potentiometers.
A3: optional analog multiplexer input.
A4, A5: SCL, SDA I2C interface.
D0, D1: UART MIDI RX and TX.
D3 or D9: optional PWM output.
D4, D5, D6 and optionally D7: multiplexer “address” outputs.

PCB Design

Key aspects of the design:

It follows quite closely the format of the Arduino Nano Mozzi Experimenter Shield PCB on the power, MIDI and Nano side.
A jumper allows the audio output to be connected to D3, D9 or neither if a DAC is plugged in.
The multiplexer’s S4 pin can be hard-jumpered to ground if required or left unconnected (or both) if not using a 4067 16-way device.
There are header pins which match the footprint of a DPDT switch to disable the MIDI link to D0/D1 to allow uploading of sketches.
The audio section of the DAC has a separate GND plane for the analog output section. If the DAC is not used this has to be connected to the GND plane of the rest of the board, so an additional connecting, plated hole is provided near to the DAC header footprint.

Closing Thoughts

I believe it is possible to use both the SSD1306 display and the MCP4725 DAC whilst servicing the other IO on the board, but I can’t imagine it would yield any practical or useful function to do so!

This is a board with options that aren’t necessarily meant to all be used at the same time. It is the latest in my line of “experimenter” boards, essentially designed for messing about with audio on the Arduino Nano.

The only thing I wished I’d added was some test points for an oscilloscope probe.

Kevin