| Eurocrack-hat | |
|---|---|
 | |
| Participants | |
| Skills | Electronics, Programming |
| Status | Active |
| Niche | Music |
| Purpose | Fun |
| Tool | No |
| Location | |
| Cost | |
| Tool category | Electronics,Eurorack |
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)
- using https://github.com/scottellis/mcp3008-speedtest I saw sample-speeds of 13k upto 36k samples per second (on a raspberry pi 2) by tweaking the block-size and the bus-speed (of course)
- 2x analogue out (12 bit resolution, MCP4922, 0.7mA max power consumption )
- 2x gate in
- 2x gate out
based oninspired by https://micro-twin.com/hardware.php
Second version
bugfixes
- CV-out range fix (caused by parallel resistors)
xth version
- more analogue in, 12 bit resolution by using a MCP3204 or MCP3208 or so?
- more analogue out, gates in
- 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:Nurd-euro-pi-001.pdf
component selection
to do
0...3.3V to -5/+5V
The opamp needs +12 and -12 for power.
Schematic thanks to Kartoffel.
-5/+5V to 0...3.3V
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
history
- 28/7/2022: ordered a few test-pcbs at jlcpcb
- 5/8/2022: problem in op-amp circuit for cv-out (output range incorrect due to resistor sharing in bias input)