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MIDI to CV converter
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alanwilder81



Joined: Sep 03, 2016
Posts: 310
Location: italy

PostPosted: Thu Jan 26, 2017 7:05 am    Post subject: MIDI to CV converter Reply with quote  Mark this post and the followings unread

hello chaps,

topic title quite self explanatory. I'm in search for a reliable circuit that converts the MIDI signal from the keyboard to CV signal in order to drive my analog monosynth.
I only need extremely basic signals. Pitch, gate, trigger. Nothing fancy.
I've seen many circuits out there to implement, i 'd love to hear your opinions and suggestions,and possibly to point me to a solid design.

i am not looking for pre made kits,they are bundled with many things i dont need. and do cost more.

thanks everyone Smile
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gabbagabi



Joined: Nov 29, 2008
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PostPosted: Thu Jan 26, 2017 9:58 am    Post subject: Reply with quote  Mark this post and the followings unread

hi alan,

if u can programm pic´s i would suggest this:
https://obsoletetechnology.wordpress.com/projects/midi-cvgate-converter/

ive build some myself, u have gate + CV + one CC ouput

if u can not programm pic´s so far but u are ready to invest not to much money in this:
http://www.piccircuit.com/shop/pic-programmer/25-icp01-usb-pic-programmer.html

iam open to help u, cos i have the same

(or on ebay, just type in ipc01, sometimes u can get it from an auction for under 10$)

cheers bb

edit: I would send u preprogrammed pics, but iam not @europe for a long time
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alanwilder81



Joined: Sep 03, 2016
Posts: 310
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PostPosted: Thu Jan 26, 2017 2:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks man,
sadly, i can't program pics, nor that circuit is suitable for my v oct synth.It's in fact a v hertz Sad Sad
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gdavis



Joined: Feb 27, 2013
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PostPosted: Thu Jan 26, 2017 3:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

An Arduino based midi to CV is pretty easy. I built one for my poly synth based on the Arduino and an 8 channel DAC.

I'm currently working on a module project based on Arduino with a 4 channel DAC and some digital outputs. I'm designing it as a flexible "utility" module that can do MIDI to CV/Gate, LFO, sequencing etc.

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alanwilder81



Joined: Sep 03, 2016
Posts: 310
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PostPosted: Thu Jan 26, 2017 4:10 pm    Post subject: Reply with quote  Mark this post and the followings unread

hey gdavis im still the ""roland guy"".here for a parallel project Cool
is that arduino project hard to make ?
i know nothing about programming that beast and i should involve a friend of mine who does arduinos a lot.
but professors are always busy,you know Rolling Eyes Rolling Eyes if it's easy to implement i might get that guy to do the job for me lol
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gdavis



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PostPosted: Thu Jan 26, 2017 5:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

alanwilder81 wrote:
hey gdavis im still the ""roland guy"".here for a parallel project Cool
is that arduino project hard to make ?
i know nothing about programming that beast and i should involve a friend of mine who does arduinos a lot.
but professors are always busy,you know Rolling Eyes Rolling Eyes if it's easy to implement i might get that guy to do the job for me lol


It helps if you know some C programming. Getting setup with Arduino is real easy, the board connects through USB and it has it's own IDE for writing programs.

The MIDI input circuit is simple and there's a software library to receive the MIDI data.

Then you just have to convert the midi note on and off messages into the proper DAC value and write it out to the DAC.

There's lots of information about how to interface the Arduino with MIDI and a DAC, you just have to put the pieces together.

I think the starter of the thread linked below has an arduino midi-CV that he built, maybe look at that:
http://electro-music.com/forum/topic-63123-0.html&postdays=0&postorder=asc&highlight=

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alanwilder81



Joined: Sep 03, 2016
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PostPosted: Fri Jan 27, 2017 3:44 am    Post subject: Reply with quote  Mark this post and the followings unread

yes gdavis,
c programming is useful and we can get arduino to do incredible things with some work and planning. To me it's all quite obscure,but i'd like to get my feet wet with it.
I took a look at the thread you linked me to.Lots of info.
has that guy succeeded in making his own MIDI to CV converter?
It looked like it was work in progress up until november, and since then he stopped posting altogether Rolling Eyes
By the way,may i ask you to show me the hardware part you built for your circuit, and also the steps you took to program it?

it's all waaaayy beyond my capabilities, but,if it's an easy job, i could get my professor friend to the job for me, assuming he gets some free time in his tight schedule Smile Smile Smile Cool Cool Cool

cheers man !
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gabbagabi



Joined: Nov 29, 2008
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PostPosted: Fri Jan 27, 2017 4:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello alanwilder,

the V/Hz function is called there "Logarithmic CV curve"

--> Logarithmic CV scale mode also known as V/Hz mode (as can be found on KORG MS10, MS20) is accessed by holding the Learn/Mode button pressed at power up. <--

- and it is a very nice PCB avaliable Cool

cheers bb
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alanwilder81



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PostPosted: Fri Jan 27, 2017 6:48 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks,
my synth is V OCT though Smile
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gdavis



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PostPosted: Fri Jan 27, 2017 2:03 pm    Post subject: Reply with quote  Mark this post and the followings unread

alanwilder81 wrote:
thanks,
my synth is V OCT though Smile


I believe he's saying that it can work in either mode - V/oct and V/Hz.

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gdavis



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PostPosted: Fri Jan 27, 2017 2:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

alanwilder81 wrote:
yes gdavis,
c programming is useful and we can get arduino to do incredible things with some work and planning. To me it's all quite obscure,but i'd like to get my feet wet with it.

I think the Arduino is a good way to get started with microcontroller programming. They simplify a lot of things for you.

Quote:
I took a look at the thread you linked me to.Lots of info.
has that guy succeeded in making his own MIDI to CV converter?
It looked like it was work in progress up until november, and since then he stopped posting altogether Rolling Eyes

I guess he got busy again. Life happens. The final version with the gate level conversion was still in progress, but I believe he had a simpler version bread boarded that was functional.

Quote:
By the way,may i ask you to show me the hardware part you built for your circuit, and also the steps you took to program it?

Mine? Oh boy. Lets see, I'll try to attach the part of the schematic from my poly. This is part of a much larger circuit for the controller board but shows the microcontroler, DAC and midi input. The modular is still in progress and a little funky.

I'd suggest getting an Arduino UNO board to start out with. Bread board the DAC and MIDI circuits and connect them to the Arduino board. Programming the Arduino board is real easy. Once the IDE and drivers are installed, it shows up as a COM port when connected. You just select the COM port in the IDE and click program. There are lots of example sketches to get started with.

I didn't implement the USB interface in my circuit. Instead I'm using the ICSP (In Circuit Serial Programming) interface to program it which requires programmer (the Arduino board can be setup as an ICSP programmer). It makes the programming a little more complicated, but not too much. For the modular I'm working on implementing the USB interface.

The DAC is connected to the microcontroller through the SPI interface (wires labelled SS, SCLK and MOSI). The Midi input connects to the serial RX input of the microcontroller (labelled RX). The two pin MIDI header goes to the MIDI DIN connector.

You'll want to put an opamp amplifier after the DAC output to scale it to the correct voltage range and buffer it. In my circuit, the amplification and buffering is actually done in a voltage controlled portamento circuit so it's more complicated.

Quote:
it's all waaaayy beyond my capabilities, but,if it's an easy job, i could get my professor friend to the job for me, assuming he gets some free time in his tight schedule Smile Smile Smile Cool Cool Cool

cheers man !

Like I said, just get the Arduino board and start learning Smile

BTW, you probably don't want to start out with the DAC I used, there are simpler and less expensive options out there.


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alanwilder81



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PostPosted: Mon Jan 30, 2017 1:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks gdavis. interesting ideas there. Smile
so, there are cheaper IC s than the one you used. i am interested in whatever does the job Cool Cool it doesn t have to be extremely sophisticated.
as long as it converts right the pitch, the gate and trigger coming from the keyboard
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gdavis



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PostPosted: Mon Jan 30, 2017 2:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ya, the 8568 is $26. Not even sure why I chose it other than wanting an 8 channel 16 bit DAC with SPI interface. Gotta say, I'm really happy with the results though, and I only needed one so I wasn't too worried about the cost.

From what I've read, you can get good tuning down to 12 bits. And if you only need one or two channels, you have many choices for just a few bucks. I would just do a google search to see what's being used most with whichever microcontroller you decide to go with so you have plenty of reference examples.

You don't need a DAC for the gate and trigger outputs since they're digital (on or off, no in between). My poly synth was designed to work with 5V gates so I could take the gate straight out of the microcontroller. If you want something like 10V for a modular, you'll need a level shifter. It seems easy in concept but often turns out to be a little more difficult to implement than people expect. There are quad and hex level shifter IC's that look easy to use (I haven't actually built a circuit using one yet).

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fonik



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PostPosted: Tue Jan 31, 2017 5:32 am    Post subject: Reply with quote  Mark this post and the followings unread

well, if you don't want to learn to code, the easiest and cheapest solution would be to use a PicKit and PIC. There are enough code file out there that you could take and write on the PIC using the PicKit. that's what i did.
me myself, i don't almost nothing about writing code, and learning to use an IDE alone makes me shiver...
YMMV

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cheers,
matthias
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alanwilder81



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PostPosted: Tue Jan 31, 2017 11:32 am    Post subject: Reply with quote  Mark this post and the followings unread

thanks gdavis. programming and digital electronics go hand in hand, and i am not particularly proficent at those Wink as you may have figured it out.
i am slowly trying to find my way through analog electronics.I have limited theoretical knowledges but it's more intuitive and more tangible than digital electronics if you will. And somewhat allowed me to succesflly nail VCO, s VCF s and so on Smile
They are two different worlds. Both interesting and complementary, indeed, though at the moment i embarked on analog and i cant have too many irons in the fire. Nor the idea of programming has ever appealed to me.
I second matthias opinion , he suggested that i get a sort of pre made kit, even a basic one,in order to save me from delving into atrocious programing art, and focus more into actual modules building.

my first take at keyboard controller module was analog. It did kinda work, but never quite as expected. In short, on key release, almost without failing i heard a pitch fall off.Pitch fluctuations experimented also on key attack.
It 's a simple project i posted a thread about some weeks ago, i got some advices on how to get it right, but no, no luck.Reason why i am looking for an alternative way.
And ,hopefully easy to implement as matthias agrees Wink Wink
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fonik



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PostPosted: Tue Jan 31, 2017 2:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

do you build on perfboard or do you prefer projects with pre-made PCBs?

i once built the midi to clock converter from marc bareille. he also has midi2CV/gate projects, which are pretty easy, i.e.
http://m.bareille.free.fr/mcv628/mcv628.html

i use a PicKit2 debug express with DIP sockets to write the hex files to the PIC. you don't even need an IDE. just write the provided hex file to the PicKit according to the pickit intructions.

don't know about the PICkit price, though. however, you could grab on off the bay, i guess.

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fonik



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PostPosted: Wed Feb 01, 2017 12:10 am    Post subject: Reply with quote  Mark this post and the followings unread

just to make your mouth water and give you some reason to buy a PicKit, here is a link to electricdruids site, where you will find quite a lot very nice PIC based projects (again, if i only had the time):
http://electricdruid.net/category/projects/

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Broadwave



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PostPosted: Wed Feb 01, 2017 1:00 am    Post subject: Reply with quote  Mark this post and the followings unread

For MIDI>CV duties, can I suggest ACX's MIDI2CV along with the latest 5.7.3 firmware.

4 Voice CV, with 8 Voice overflow ability, great mod output options in mono mode. All my analogue synths have one built in now.
You can also buy a basic PCB kit with programmed PIC from Hexinverter.

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fonik



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PostPosted: Wed Feb 01, 2017 1:17 am    Post subject: Reply with quote  Mark this post and the followings unread

^^ Oh, i can second that. in fact i built a beta test module for Hexinverter back then!
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Cfish



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PostPosted: Sat Feb 04, 2017 9:15 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Alanwilder81

If you have not came up with something, and cost is the obstacle.

I did mine with an arduino nano clone 3 dollars US a 2 dollar shift register, a resistor ladder using .1% resistors for DA conversion. Then a TL074 for adjusting the analog and a TL072 to add glide.

Glide can be left out.

I can send you a link to the code I used. You can dump it on the nano with a USB cable.

If you want, let me know, and I will dig out my schematic.


Edit. Oh and Ray Willson MFOS has one on there sight with all fixed ICs. No programming.

However it has a lot of parts.
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ejr27233



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PostPosted: Sun Feb 05, 2017 1:42 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi Cfish
I came across this thread while looking to see if it is possible to build an arduino with R2R.
If you Could you send me your code and a schematic it would be great.

Thanks in advance,

John
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Cfish



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PostPosted: Sun Feb 05, 2017 8:38 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi ejr27233

Here we go. Sorry the schematics are crude. I drew them as I was figuring out board layout.

I need to give credit where credit is due.

The analog section is a semplified version of an early Ray Willson MIDI to CV

The digital section was created mostly by my brother.

I am posting schematics now. I half to reload a few code versions later today to make sure I don't give you the wrong one. Had several with glitches. The code is from my brother.

This is tested and works well.

Schematic is divided in to 2 pages. Analog and digital sections.


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Cfish



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PostPosted: Sun Feb 05, 2017 8:58 am    Post subject: Reply with quote  Mark this post and the followings unread

And this is a simple alternate analog section with no bells and whistles.

I liked using it to get things working.

I'm not 100% sure but I think I modified this section from an old CGS schematic.

I always used .1% resistors in the ladder. Most only call for 1%

I'm not sure if the overkill helped, but it can't hurt. Mine tracks very well.

Will also include a picture of mine on perf. I kept things spread out so I had plenty of room to work and experiment.

My modules are actually even larger than 5u. I had made up my mind I didn't want to half to cram things when I started down the modular path.

Years of guitar pedals had me tired of cramming things.

I am running on 15v+- but I was able to track the volt per octave in on 12v+- with no problems at all.


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Cfish



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PostPosted: Sun Feb 05, 2017 9:07 am    Post subject: Reply with quote  Mark this post and the followings unread

One thing this really needed was a trigger added.

Asked my brother to add it in the code before I put it out.

Will just need a duplicate gate analog section tied to the next IO pin.

The gate does not retrigger untill key release on the current code.

Going to add trigger to mine while I have it out of the rack.
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ejr27233



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PostPosted: Sun Feb 05, 2017 12:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Your simpler version is exactly what I was looking for.
Many thanks
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