Midi2CV Mk2 is a DIY embeddable MIDI to 4 x CV/Gate converter with reasonable defaults and extensive configuration options.
- +-12V or +-15V, Euro or MOTM power connector
- 50mA@+15V, 10mA@-15V
- 4 x CV channels, each could be 0+5V, 0+10V or -5+5V, configurable by jumpers
- 4 x Gate channels, 0+5V, 0+7V or 0+10V, configurable by a jumper
MIDI IN LED
- optional MIDI IN LED, blinks when receiving MIDI events
- optional GATE LED, lit when a note is on
- MIDI IN connector
- optional MIDI OUT connector, mirrors MIDI IN
- held down during power up — enters firmware update mode via MIDI
- held down while receiving control change, after touch or program change events — learns control CV parameter
- held down while moving pitch wheel up/down — turns note tuning mode on and off
- held down for 10 sec while the device is idle — resets the device to defaults
ON-BOARD DIP SWITCHES
SW1-4 specify base MIDI channel
- MONO and DRUM modes use the base channel
- DUAL mode uses base channel and base channel + 1
- QUAD mode uses base channel, base channel +1, +2 and +3
SW5-6 specify operation mode:
CV: note, velocity, pitch bend, control
Gate: gate, strobe, start, clock
CV: note, velocity, note2, velocity2
Gate: gate, strobe, gate2, strobe2
CV: note, note2, note3, note4
Gate: gate, gate2, gate3, gate4
CV: velocity, velocity2, velocity3, velocity4 pulses
Gate: gate, gate2, gate3, gate4
Note CV: 1V/Oct pitch CV with optional micro tuning: every note can be set to output any CV level within selected output range. Can be used for Hz/V, alternate tuning schemes, or to correct VCO tracking imperfections. Note tuning is set using special mode of operation, and could be saved, restored or specified by a sysex.
Velocity CV: linear by default, however you can choose to adjust velocity response curve making it softer, harder or wider:
Control CV: by default, this CV tracks CC 1 (Modulation Wheel) value, however it could be set to track any CC from 1 to 119, or after touch/program change values. If set to track after touch, the response curve could be adjusted similarly to velocity response curve. Control setting can be “learned” on the fly: hold down LEARN switch and turn/click the desired control knob/button, or press a key on after touch-enabled keyboard to track after touch.
Gate: goes high when a key is down, low when no keys are down. If “strobe gate” option is in effect, gate signal is pulled down for the duration of the strobe every time a key is pressed while some other key is down. This allows envelopes to re-trigger for synths that don’t have Strobe input.
Strobe: goes down for 1 to 5 ms, occurs each time a key is pressed. Strobe length and polarity are configurable by sending a sysex message and the setting is persisted in EEPROM.
Start: goes high when MIDI Start/Continue message is received and down when MIDI Stop message is received.
Clock: goes down for 1 to 5ms each time MIDI clock message is received, could be divided down to 32 triplet, 32th note, 16 triplet, 16th note, 8th note triplet, etc. all the way to 2 bar note. Division factor is configurable by a sysex and the setting is persisted in EEPROM.
In DRUM mode CV outputs produce gate like signals with amplitude proportional to the note velocity. The unit response to 4 predefined notes (by default C3,C3#,D3,D3#) on the base channel. The notes can be configured via sysex and are persisted in EEPROM.
Note CV tuning
The default note CV tuning is 1V/Oct for output range 0-10V and -5+5V ranges, and 0.5V/Oct for 0-5V range.
To enable note CV tuning mode hold down LEARN switch and move Pitchbend wheel up, then release LEARN switch and return Pitchbend wheel to neutral.
To disable note CV tuning mode, hold down LEARN switch and move the Pitchbend wheel down, then release LEARN switch and return Pitchbend wheel to neutral.
While note tuning mode is in effect, hold done a note and use pitch wheel to adjust its pitch. Release the note to remember its pitch.
You can also use Control Change messages to reset, increment/decrement and interpolate note tuning, see the CC table below.
Control Change messages
While in note tuning mode Midi2CV Mk2 recognizes the following control messages:
|115||> 0||Reset all notes tuning|
|116||> 0||Reset last note tuning|
|117||> 0||Increment last note tuning|
|118||> 0||Decrement last note tuning|
|119||> 0||Interpolate last note tuning|
You can also use pitch wheel to quickly get note tuning into required range.
Sysex data format
Sysex message format:
0xf0, // Sysex
0x29, // PPG manufacturer ID
'2','C','V',0x00, // Midi2CV Product ID
// * Command byte (SysexCmd)
// * Argument byte (flags | index)
// * Payload bytes (nibbelized)
0xf7 // Sysex end
Sysex message commands:
0x00, // arg=0 reset device, arg=1 update firmware (v1.14+)
0x01, // set controller cc number or 128=AT, 129=PC
0x02, // set strobe width 0-4: 1-5ms
0x03, // set clock divider 0-19: see intervals.h/cc
0x04, // set tune data 128 x int words of tune data
0x05, // set velocity curve, 0-8: linear, soft1/2/3, hard1/2/3, wide1/2
0x06, // set aftertouch curve, 0-8: linear, soft1/2/3, hard1/2/3, wide1/2
0x07, // set 4 x drum notes, 0-7f (v1.10+)
0x08, // set invert strobe mode: 0 - positive, 1 - negative (v1.11+)
0x09, // set invert gate mode: 0 - positive, 1 - negative (v1.12+)
0x0A, // set strobe gate mode: 0 - off, 1 - on (v1.13+)
0x10, // request firmware version (v1.11+)
0x11, // request SETCONTROLLER
0x12, // request SETSTROBEWIDTH
0x13, // request SETCLOCKDIVIDER
0x14, // request SETTUNEDATA
0x15, // request SETVELOCITYCURVE
0x16, // request SETAFTERTOUCHCURVE
0x17, // request SETDRUMNOTES (v1.10+)
0x18, // request SETINVERTEDSTROBE (v1.11+)
0x19, // request SETINVERTEDGATE (v1.12+)
0x1A, // request SETSTROBEGATE (v1.13+)
Midi2CV firmware update steps:
- Connect your MIDI interface output to Midi2CV MIDI IN
- Power on Midi2CV while holding down LEARN switch. LEDs will blink shortly then MIDI IN LED will stay steadily lit.
- Send firmware update sysex file (*.syx) to your MIDI interface port with 250ms delay between sysex buffers. Elektron’s C6 works great on OS X and Windows. Classic MIDI-OX is also good on Windows. MIDI LED will be blink while firmware sysex is being received. On successful update, LEDs will blink 3 times one after another. On error, both LEDs will blink together 5 times.
Starting with firmware version 1.14 you can request firmware update without using LEARN switch by sending RESET DEVICE sysex with argument byte set to 0x01. This facilitates firmware updates for applications where LEARN switch is not present or is difficult to access.
- Set note CVs to C4 upon start or reset
- Added ability to request firmware update by sysex
- Added “strobe gate” option and sysex
- Added gate polarity option and sysex
- Fixed problems with All Notes Off handling
- Added strobe polarity option and sysex
- Added firmware version request sysex
- added Drum Mode
- changed Note Tuning mode activation to LEARN+PitchBend
- fixed nasty EEEPROM initialization bug
Bill of Materials: Midi2CV Mk2 BOM
Sysex files: midi2cv_mk2_sysex_114
Firmware source code: midi2cv_mk2_112_src
Board outline (1:1 PDF): midi2cv_mk2
To order Midi2CV, please send an email to pete at kvitek c o m specifying how many PCBs and pre-programmed MCUs you need, a country where to ship them, and an email address to send the PayPal invoice to.
Prices (US dollars):
Midi2CV PCB — $25
Pre-programmed ATMega328p — $10
Continental USA — $5 (California residents add 8.75% tax)
Canada – $10
Europe – $15
Australia – $15
Please make sure your PayPal shipping address is correct!