Nurdspace eurorack raspberry pi hat: Difference between revisions

Latest revision as of 07:28, 6 August 2022

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)
- 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 on~~inspired 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

eurocrack opamp

to do

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

falstad circuitjs simulation

The opamp needs +12 and -12 for power.

Schematic thanks to Kartoffel.

-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

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)

@@ Line 22: / Line 22: @@
 * 2x analogue out (12 bit resolution, [https://ww1.microchip.com/downloads/en/devicedoc/22250a.pdf 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)
+* 2x gate out
-* <s>based on</s>inspired on https://micro-twin.com/hardware.php
+* <s>based on</s>inspired 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 [http://ww1.microchip.com/downloads/en/devicedoc/21298e.pdf MCP3204 or MCP3208] or so?
 * more analogue out, gates in
-* also gates out
 * LEDs for gate status
 * pins for neopixel connection (gnd + signal)
@@ Line 49: / Line 53: @@
 === 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 ===
-[https://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWEAOAnLAzKgbBsqB2AJiMgwwBYQsQkKNaBTAWjDACgBDEIhbHyMmrIqpIalohmSMPHg9oRMNlSoiFXEvJgGRRWAJllFIqjYiwMuZHYAnHnx7Fho55Gpz2Adwf8SoxyI3bxcBIQwRJyIoO19wNXAKKnxo93I4WN5+MCJwyJyhd1l4dgBzUIKK7HcakKzwXLiUmIAlROSE5CKkqHAQCiLobBkhpBroBFiwHv92jyp3UhLy6aoMSGSe8n5a+1WedX6hWcXPNopjw9Y-Q5r+tOgGO5hJn33Z+pPYiNFBI9PCuASj4LgDaI0xDEAPbUEDYBb3VRAqCwOD4BB4Xi9aIMDDsGGWOEIgZIsaouCEYbYLEQaKEvFAA falstad circuitjs simulation]
+[https://www.falstad.com/circuit/circuitjs.html?ctz=CQAgjCAMB0l3BWcZYA4BsB2ATNzZsEBOVA9EBSCiqhAUwFowwAoAQxAGZUAWEI8ggL9yqcFSZUw8eF2hgimHp0ioEuPDzCZMchUsxYl6dYqLiZLAPIVhAkOlUjwUdiAadsXL-c8gxSAxI0jJU2NBI4ZRwhPCxMeQh8CwA7u5+PGIePuSQqek5zvZ5afZl5H55AE7u9mDkDPaoVFKWNY0NmbWJuRZwLABK3e5dTI4jYi0gPLRQczAILADmw83Dxa5p2eANdbn5KnzaFbzIXtUghBVenOhilX0X3Hx+Qjfnl5Zpt-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-Q1MVrbVR1w2tMk7WiR00xrGM5U2ENdXkJgCEFokrgcD1xw1Vkh1iNIImPKJAb6MoqjqLgSjaIJ8iKHJRiOqYmAYBd+QFb1dqtvUYK-YD9hjGCoMg9crgEi49FzDMJDiFA8hzKwQA falstad circuitjs simulation]
-The opamp needs +5 and -5 for power (the -5V can be obtained by using an ICL7660 ic).
-calculated with https://masteringelectronicsdesign.com/differential-amplifier-calculator-2/
+The opamp needs +12 and -12 for power.
-Also see discussion at https://electronics.stackexchange.com/questions/628874/converting-dac-voltage-to-eurorack-voltage
+Schematic thanks to Kartoffel.
 [[File:Circuit-20220715-2051.png|640px]]
@@ Line 80: / Line 79: @@
 * 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)