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MIDI
to CV-Gate Interface MCV-628
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To
drive analog monophonic CV/Gate synthesizers with MIDI devices.
Schematic
and pcb
This interface
is builded with a PIC16F628 clocked at 20MHz. the hardware.
The PIC16F628 have an integrated USART ( serial Port ) also
the MIDI port is not a software emulation of the serial port
, but a real hardware implementation. Unless to say its more
reliable and faster compared to a PIC16F84 at 4 MHz emulating
serial port ...The voltage reference is a REF01, more expensive
than the TL431, but no need of trimmers & resistors to get
a stable +10V reference voltage... For CV output amplifiers
i get good results with the LF412 (<+2mV offset) or LM358
( -1mV!!! ), but most of dual amplifiers work well here. Best
one here are precision low drift, low offset ..Trimmers near
aops are here to adjust CV scale to 1V/Oct or 10V full scale
. They are optionnal , but it is better to keep them for fine
calibration of CVs outputs. The interface must be powered by
a well regulated +/-15VPSU
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Firmware
for PIC16F628
The main piece of code, the brain of the interface. To
download and "burn" into the PIC16F628. Choose the firmware
according to your need, again many hardware compatible
versions are available.
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MCV-628
firmware v1.12P
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1V/Oct
or 48 notes table editable by sysex for V/Hz
or others AuxCV assignable to Velocity or any MIDI
controlers. Gate is positive logic (0=off,
+5V=on) Autolearn for channel, Note ref ( transpose),
controler number for AuxCV. All parameters for this
firmware can be edited in real time with sysex messages.
)
Here
is the generic asm source
code MCV628 v1.12
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MCV-628
firmware v1.12N
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Same
as v1.11P but with negative logic GATE
for KORG MS10, MS20 synthesizers
(0=on, +5V=off) Note : the Gate Led must be reversed
on pcb with the anode connected to +Vcc (and not
GND ) to work correctly .
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| MIDICLOCK
628 firmware |
to transform
the MCV628 into a MIDI Clock converter/divider
like the MC628.
The clock pulse signal is present at the gate
output..The PC config software for the MC628 can
be used to edit parameters.
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| Blink
Test MCV628 Program |
This
useful file is to try if the PIC is ok. Blink
Test source code(ASM)
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The
GATE led
It
is a multi purpose led! It blink 3 times at power on,
after the complete init of the cpu/software. It means
"All is ok". In normal working condition, the Gate
led ligth when a note is played or if a recognised SysEx
message is received. If a trouble happen during SysEx
reception, the led will stay on, showing an error has
occured. Nothing is written in Eeprom in this case. Any
incoming MIDI message will unlock the interface, else
it is a fatal error from the PIC, and a cold reset is
may be necessary ( very rare case). When the interface
is in Autolearn mode, the Gate led stay on, until
a MIDI message has been received.
Autolearn
Mode
It
is the simplest way to set main parameters of the interface.
Here
how it works: Push
Autolearn switch on the interface, the Gate led
ligth on. The interface is now in Autolearn mode
waiting for the next MIDI message you will send. When
the interface receive the message, MIDI channel, note
or controler informations are extracted and stored to
the Flash memory of the interface. One parameter only
is changed at time. The led gate goes off and the interface
is now setup with the new value...That's all! Parameters
changed by the Autolearn mode are :
- MIDI
channel number : 1..16 . Send any MIDI message
with channel number inside.
- Reference
note : 0..127 Lowest note
the interface can play ( digital zero) Send a note
message
- Reference
controler : 0..127 The contoler number
assigned to AuxCV .Send a controler message
MIDI
implementation
Note
On
NoteOff
All note off |
Pitch
CV
Note stack for true last note played operation
Running status implemented. |
| Controlers |
firmware <1.1 : AuxCV wired to Mod
Wheel ( control 1)
firmware
>1.1 : AuxCV assignable to velocity
or any controler
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| SysEx |
format
<F0,ID,CAN,ADR,LSB,MSB,F7>
Covers all firmware parameters + 48 notes
table stored in Flash eprom. ( only for firmware
rev> 1.10) |
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The
PC Config Software
With
firmware revision upper than 1.1, the MCV628 memory is fully
editable with MIDI exclusive messages.I have written a complete
MCV628 editor software for PC under Windows 9x /XP. Very helpful
to the
interface, with few mouse clics...
IMPORTANT UPDATE read here :
Here is a new version of the PC Config Editor for the MCV628. . It replace the V1.1 who seem to do not work anymore with the actual firmware ...I must say that i have loosed the v1.1 source in a hard disk crash few time ago . So i have quickly re-writen it from scratch ... Indeed i have not implemented the table 'feeding' featurre . This software is mainly useful to setup the 1V/Oct mode just after you have burned a new firmware into the PIC - by default it is table mode who is no more used here and see to put in trouble many builders ;) So use the V1.2 Editor with the actual 1.12 firmware .
MCV628 config software V2.8a for PC (unrar , no install required )
For your knowledge ,the table feature is not very useful excepted under very rare situations. V/Hz synths like Lorg MS10/20 should be driven with at least a 12Bits dac like here . Pure 8 bits interfaces like he MCV628 are not enough accurate to emulate a smooth enough expo scale .
The MCV628 is perfect to to drive any 1V/Oct synthesizers like Moogs , Arp , Roland, SCI, or modular VCOs with an excellent accuracy .
Old version !!! - do not use - for archive and the rare diyers who still have a compatible firmware
MCV628 config software V1.1 for PC
Here
are screen pictures of the config software v1.1..., the new one is not very different unless there is no more the table feature .
The 48 Notes
Table tune editor: the special CV scale showed is to drive
a Thyratron tube VCO (2D21) with MIDI in my X2TS
tube synth.
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MCV628
pcb + construction manual
are available
on order
Last Update 17/03/2010
Released in 2003
©
Marc BAREILLE 2003-2010
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