Kicad-MidiToCV

Midi to CV in Eurorack

MK2 Design

Status - PCB delivered tested

Initial

Stage	Detail	Status
create material	sch/pcb	produced MK2 Rev A
	gerber	Produced MK2
production	ordered
	produced	yes
	delivered	yes

Preliminary validation

Test	Detail	Status
Initial Inspection	conflict between LED on front panel and optional CV7	OK
Initial Technical Test		OK
Initial Product Test		OK!
	LED's	OK
	Encoder	OK
	CV1+CV2	OK
	GATE 1,2,3,4	OK
	MIDI I/O	OK

Secondary validation

Test	Detail	Status
Product Test
Quality
Long Term Product Test		Mounted in rack

Software

Test	Detail	Status
Initial SW	copy from MK1 and adjusted	OK!
MIDI I/O	UI
MIDI I/O	Filtering and change ch
CV Control	UI
CV Control
LFO Control	UI
LFO Control	Function

Errata

• Physical mounting of the faceplate to holes on the base plate requires other dimensions of the angled mounts. The mounts can be very difficult to get in place due to limited space behind the front PCB.

Issues and Notes

• Note - the 4 value LED's are routed across the front board next to analogue and gate signals - so care should be taken when deciding between constant power or PWM control of brightness. The other LED's are not considered as vital as they will normally be lit when config is changed.
• Consider replacing single row board connector with double row.
• Physical construction not finalized

Workarounds

Base Construction

Arduino base board

• Arduino Nano
• MIDI IN/OUT connectors
• CV 1 and CV 2 as Mini Jacks (PJ-301) with variable x2-x3 amplification and 1st order LP filter
• Gate 1 and Gate 2 as Mini Jacks (PJ-301) 5V
• Gate 3 and Gate 4 as Mini Jacks (PJ-321) with fixed x2 amplification and sallen-key LP 2nd order filter
• Board connector 9pin and 11pin from base board to front board
• 16pin Europower connector
• Barreljack for 7-12V digital Pwr

Vital Components

• Arduino Nano - where the magic lives (remember to socket it to be able to reprogram it - two jumpers are in place for Rx/Tx so socket may be avoided)
• Jack connectors: PJ-321 for the base board and PJ-301 for the front board (important for the footprint)
• ALPS EC-11 Encoder (important for the footprint and 3D alignment)
• ALPS RV09 horisontal potentiometer (important for the footprint and for variable CV out - can be omitted if this is not needed)
• MCP4825 module - if chosen (important for CV out function - footprint needs to match)
• TL072 or similar dual op amp

Mechanical

The construction is still split in two - but the MK2 design relies on a base board that is 90degrees to the face plate (like the MK1) and a connector board that is 10mm behind the faceplate 90 degrees angle to the base board.

MK1 Design

Status - Rev B - Ongoing PCB layout and Sch update

Status - Rev A Mounted - Midi code in progress

Issues and Notes

Please note that the PIN1 and PIN2 are GATE. This is note described clearly in http://www.doepfer.de/a100_man/a100t_e.htm and needs to be noted when soldering the IDC header or when cabling if a Pin header has been mounted.

• The two pots on the breakout board are too close for adding a knob
• The orientation of the pinheader for the MCP4725 module - if mounted incorrectly the magic smoke disappears
• 0R could be replaced with SMD jumpers
• Consider a 200 mA fuse for Vin and 50mA for +5V pwr
• The mounting hole that is off center is not matching both boards

Errata

• Footprint of PJ-321 has too small drill holes (1mm) - major
• Footprint of PJ-321 is too narrow in the rear end :) - minor issue
• Midi out circuit is WRONG - Major

Workarounds

• Midi out not working - PCB workaround mod partially possible
• --Remove GND around DIN pin 5 (bottom copper side)
• --Cut GND track to DIN pin 5 (top copper side)
• --Remove Q1, R6, R9
• --Connect 220R THT to base pad on Q1
• --Connect C and E on Q1
• --Add GND wire to pin2 of MIDI out DIN

Physical Construction

• 100x100mm
• Separate unit with no alteration
• Optional split in 2 for eurorack mount mirrored config

Vital Components

• Arduino Nano - where the magic lives (remember to socket it to be able to reprogram it)
• Jack connectors: PJ-321 (important for the footprint)
• KY-40 Encoder module (important for the pullup, footprint and 3D alignment)
• MCP4825 module - if chosen (important for CV out function - footprint needs to match) If these are chosen the last two CV jacks should be ommitted.
• MCP4728 chip - if chosen (important for the last 2 CV out)

MIDI Board Features

Single board - MIDI I/O and MIDI to CV

The board can be used as is for a prototype development of MIDI to CV

Split board Eurorack - MIDI I/O and MIDI to CV

The board can be devided in two and combined front to front with spacers for a MIDI to CV eurorack module.

Base board Eurorack - MIDI I/O

If only MIDI features are required the base board can work without the IO section.

Generic Board Features

Split board Options

The main board (with the arduino) has a couple of headers that can be connected to a different interface board using I2C, Analogue Inputs and Digital I/O.

Non MIDI board

The MIDI components can be omitted if the features does not require MIDI, like an LFO, VCO or ADSR circuit.

Base Construction

Arduino Nano based Controller and MIDI decoder.

MIDI In

MIDI In through a PC814 (or optional PC817) Optocoupler and into the RX pin on the Arduino

Midi Out

Optional expansion

Gate

Gate pins from Arduino

CV Out

I2C Dac with 2 options

I2C Dac - Option 1 - Two Single channel DAC

2x MCP4725 DAC

I2C Dac - Option 2 - One 4 channel DAC

1x MCP4728

RevB

RevA