Nurdspace eurorack raspberry pi hat

Eurocrack-hat
Participants
Skills	Electronics, Programming
Status	Active
Niche	Music
Purpose	Fun
Tool	No
Location
Cost
Tool category	Electronics,Eurorack

Eurocrack-hat

Nurd-euro-pi.jpg {{#if:No | [[Tool Owner::{{{ProjectParticipants}}} | }} {{#if:No | [[Tool Cost::{{{Cost}}} | }}

specifications

This will be an interface between eurorack signals ("control voltage" and "gates", all in the Doepfer range of -5V...+5V) and a raspberry pi (a "hat"). For that, the hat will have an ADC and a DAC (multichannel) connected via SPI (multichannel and not multiple devices as the rpi has only 2 SPI channels).

First version

• 2x analogue in (10 bit resolution, MCP3008, 0.5mA max power consumption )
• 2x analogue out (12 bit resolution, MCP4922, 0.7mA max power consumption )
• 2x gate in
• being able to also run without a real eurorack powersupply (it produces its own -5V by using an ICL7660)
• based oninspired on https://micro-twin.com/hardware.php

Second version

• more analogue in, 12 bit resolution by using a MCP3204 or MCP3208 or so?
• more analogue out, gates in
• also gates out
• LEDs for gate status
• pins for neopixel connection (gnd + signal)
• I2C breakout (for e.g. small displays)
• SPI extender? (does something like that exist?)
• SMD technology maybe?

schematics

• Kicad files: see github

• PDF of revision 001: File:001.pdf

component selection

• eurocrack opamp

to do

• double check 3.3V power consumption of parts

• check if a MCP6001 opamp can withstand not only -5/+5 but also -12/+12V

0...3.3V to -5/+5V

falstad circuitjs simulation

The opamp needs +5 and -5 for power.

calculated with https://masteringelectronicsdesign.com/differential-amplifier-calculator-2/

-5/+5V to 0...3.3V

falstad circuitjs simulation

The opamp needs +3.3V and 0V for power.

software

• I've chosen a DAC and ADC with SPI to easily connect them to a raspberry pi.

• gate signals can be toggled via e.g. wiringpi