OPERA ROTAS, a DIY mutant drum machine BUILD THREAD

[nina_nothing]

Hey

Just got this little beast at thursday. And, as expected, i really love it. Took it to band practice and put it through my absurdly large wall of amps. It was pure happiness.

But let's stop bragging. Am i missing something or is there not a way to stop the sequencer?

Thanks for any answer

[SphericalSound]

Glad you like it and welcome to MFs!

Yeah, there´s no way to stop the sequencer and it will be like this for at least quite time, but there will be some future update addressing this and other things and ideas

What combination of keys would you use / make sense to start/stop the sequencer?

[yan6]

Ontop of stopping the sequencer, another nice to have would be a way to clear the pattern

[Bodo1967]

And - ability to sync to an external clock provided - a mute function (as, for instance, in the Beatstep Pro) so it stays synced while not putting out sound.

[nina_nothing]

What combination of keys would you use / make sense to start/stop the sequencer?

Well, i was thinking about implementing this myself. Shift + rec crossed my mind. Also i wanted to make the bpm range much much larger - specially under like 50 bpm.

Hmm, if you agree, i can take a look at the code during holidays and i can try to implement it.

Anyway, i have managed really primitive way how to use control voltage from modular synths to move knobs on opera rotas. If anyone will be interested, i can write more about it or i might even draw a schematic.

[SphericalSound]

Yeah, sure we will like to see that schematic.

Send me your mail address in a PM for me to send you the source code

<quote>Ontop of stopping the sequencer, another nice to have would be a way to clear the pattern</quote>

This and mute/unmute channels are quite asked and will be in the next code iteration. The problem is not coding it, which is more or less trivial, but how to do that you, the user, can update the firmware without having to compile it. It is almost there

The analog clock in seems that will work too, fingers crossed

[Bodo1967]

<quote>Ontop of stopping the sequencer, another nice to have would be a way to clear the pattern</quote>

This and mute/unmute channels are quite asked and will be in the next code iteration.
The analog clock in seems that will work too, fingers crossed

That. Sounds. Awesome!

The problem is not coding it, which is more or less trivial, but how to do that you, the user, can update the firmware without having to compile it. It is almost there

Using the STLink device mentioned earlier in the thread would be cool. They are really cheap (I already bought one, cost me about 3 Euros).
In my not-able-to-code-idiot view, something like this ...

1. Download the ready-for-use firmware.
2. Copy it to the STLink which is connected to your computer via USB.
3. Disconnect the STLink from your computer and connect it to the OR.
4. Press <buttons>, do a ritual dance with the following steps, wait for <message> on the display, et voilà!

... would be super great and easy. OK, perhaps without the ritual dance .

[NS4W]

This and mute/unmute channels are quite asked and will be in the next code iteration. The problem is not coding it, which is more or less trivial, but how to do that you, the user, can update the firmware without having to compile it. It is almost there

The analog clock in seems that will work too, fingers crossed

All I want for Xmas...

[SphericalSound]

Ok, more updates. Mixed news. It happens that for you to update the code you need a .hex file to upload to your bluepill via the st link v2. Easy.

Platformio is producing .bins intead of .hex, hence it were not working.

There´s some guides on how to signal platformio to compile the .hex too, but are outdated and my current platformio version does not have this option.

There´s an alternative way to do it, doing some python scripting, but when I add the script my code stops to compile correctly... So now Im looking for some platformio/python expert that explain me how to run the script...

I know we will get to it but theres alway some inexpected surprise... so please keep be patient and go get one st link v2 programmer in ebay in case you dont have one yet. It costs 2-3usd and looks like this:

[SKYNET_23]

THANKS FOR Keeping the flame alive... Of course MIDI would be nice, but i'm down with analog clock sync, i have an ST Link, and i'll keep checking back here for updates. Good luck too all, and thanks again!

[Bjarne]

Hola!

If I'm not mistaken (I may very well be) it could be feasible to replace the 4n35 with the more commonly used 6n137 optocoupler. This would of course take some hardware patching, but it would not have to be a completely separate board (more of an adapter), right?

I'm sure I will enjoy the Opera Rotas even without MIDI, but I think for firmware patching and future expandability (e.g. a synth modification), MIDI capability would really make a big difference.

Merry X-mas and Happy new year!
B

I have bad news for you.

After a lot of testing I have discovered that the optocoupler that Opera Rotas uses (4n35) is not fast enought for MIDI transmision.

Somebody did a tutorial using this opto, I followed the hardware and after a lot of testing, yesterday I discovered that the 4n35 is too slow, so it did not work and pretty much it wont have MIDI. Sorry guys, Im the first that I would love to midify it and play with a keyboard. In kind of obsessed with it, but as the machine is set up you cant get it.

In the meantime, if somebody has any idea: maybe bypassing the optocoupler and conecting the midi cable directly to the microcontroller doing some 5v>3.3v voltage division? or something like?

Im all ears

Regarding analog clock input is quite easy with a bit of hacking. Maybe you can use the MIDI in port to do it. I can prepare binaries with this mod, but I havent found a way to distribute it and load into the microcontroller. To date the only way I have found to write the micro is compiling via arduino IDE or Platformio. With the .bin compiled it just dont want to upload via st link nor via USB.

Again, if somebody knows how to do it, Im all ears.

[Bodo1967]

If I'm not mistaken (I may very well be) it could be feasible to replace the 4n35 with the more commonly used 6n137 optocoupler. This would of course take some hardware patching, but it would not have to be a completely separate board (more of an adapter), right?

Sounds tempting, but I don't think that would be easy or even possible since the 4n35 has six pins, and the 6n137 has eight .

[Bjarne]

That's what I'm referring to as hardware patching. That part is not hard to do.
B

If I'm not mistaken (I may very well be) it could be feasible to replace the 4n35 with the more commonly used 6n137 optocoupler. This would of course take some hardware patching, but it would not have to be a completely separate board (more of an adapter), right?

Sounds tempting, but I don't think that would be easy or even possible since the 4n35 has six pins, and the 6n137 has eight .

[Bjarne]

Below are some excerpts of the Opera Rotas current use of 4n35 vs common use of 6n137 optocoupler. As I proposed, a small adapter and some hardware patching would be needed to re-assign pins and some of the output circuitry, but I guess it should be manageable using a small protoboard.
Then of course, the actual midi implementation needs to be completed in the firmware.

Cheers

4n35-vs-6n137.png (17.08 KiB) Viewed 211 times

[SphericalSound]

Yeah I meant a small adapter, like a midi in chiclet.

I still havent found a way to export .hex files from platformio... so enjoy it as it is now. It will happen in the least expected eureka moment in 2021

[NS4W]

I still havent found a way to export .hex files from platformio... so enjoy it as it is now. It will happen in the least expected eureka moment in 2021

Have you tried this? ---> https://community.platformio.org/t/expo ... x-file/939

[Bjarne]

Yeah I meant a small adapter, like a midi in chiclet.

[Bodo1967]

That's what I'm referring to as hardware patching. That part is not hard to do.

As I proposed, a small adapter and some hardware patching would be needed to re-assign pins and some of the output circuitry, but I guess it should be manageable using a small protoboard.

Ah, OK, thanks!
I had assumed this would be difficult due to lacking space, but I agree it might be possible (I don't have much height reserve though, since I gave mine an acrylic front cover plate limiting the free space, but of course that's just my "problem" and not anybody elses's ).

However, if internal hardware patching (which I agree would definitely be the more elegant version) ever should not be doable, some external device would also do - at least in my personal case:

Perhaps something like bypassing the optocoupler and using a small external interface box based on an 6N137 or similar that accepts MIDI in from a sequencer

[Bjarne]

Agreed. In this case the required patching is so minimal that a small chiclet adapter that plug into the 4n35 together with bridging/removal of the then unnecessary R1/R17 resistors will work a charm (but it will add a little height). The good thing is that the majority of the existing pcb wiring for midi will still be in use and an external board won’t be necessary.
Cheers

However, if internal hardware patching (which I agree would definitely be the more elegant version) ever should not be doable, some external device would also do - at least in my personal case

[SphericalSound]

I still havent found a way to export .hex files from platformio... so enjoy it as it is now. It will happen in the least expected eureka moment in 2021

Have you tried this? ---> https://community.platformio.org/t/expo ... x-file/939

Yep. That was my first attempt. I have like 200 main.py files inside that folder or sumthing. I will try again...

[SphericalSound]

I still havent found a way to export .hex files from platformio... so enjoy it as it is now. It will happen in the least expected eureka moment in 2021

Have you tried this? ---> https://community.platformio.org/t/expo ... x-file/939

Aaand... I have tried this again. It happens that the tutorial has slightly wrong folders name... After tweaking a bit, this is the right folder name to force platformio to export .hex:

C:\Users\Admin\.platformio\platforms\ststm32\builder

So now it compilles to .hex and finally I can distribute the hex for you to update. So thank you for pointing it. The update procedure is dead easy and takes 2 mins. You will need an st link v2 gadget and the "st link utility" software provided by st link. You have to open a free account with them to download it. Get it as updates are coming

https://stm32-st-link-utility.software. ... /download/

[Bodo1967]

I don't have much height reserve though, since I gave mine an acrylic front cover plate limiting the free space

Cutting and drilling that plastic material is definitely not my favorite pastime , and it will never be.

The Opera Rotas just sits in the black wooden stand I made, it's not mounted firmly there.

[SphericalSound]

I don't have much height reserve though, since I gave mine an acrylic front cover plate limiting the free space

01IMGP3717.jpg


Cutting and drilling that plastic material is definitely not my favorite pastime , and it will never be.

The Opera Rotas just sits in the black wooden stand I made, it's not mounted firmly there.

That´s fucking beautiful. It seems like Rotas' has 50 years or sumthing.

I have an update ready, by the way. The new firmware does:

-press REC + channel 1-8 to toggle mute/unmute channels
-press SAVE + channel 1-8 to clear the pattern of the selected channel
- it announces firm 1.1 on startup

Take it as a beta. If you want to betatest and speak "stm32" fluently (so you have the st link utility installed and worked previosusly with bluepills) just ask for the .hex via PM

The analog clock in does not work with the current optocoupler. For the midi in chiclet I have ordered some 6n138 optocouplers. The whole midi expansion pcb could take 8 weeks or more from prototiping to final version so dont hold your breath.

Finally Opera Rotas is going open source. I just have to clean a bit the code. It should be released in a few days

[Bjarne]

Wow,

all of the above sounds great! Any reason for going with 6n138 instead of 6n137?
Edit: the reason I’m asking is that I’ve seen several recommendations for 6n137 over 6n138, e.g. https://forum.mutable-instruments.net/t ... plers/5255

Happy (better) new year

[SphericalSound]

Wow,

all of the above sounds great! Any reason for going with 6n138 instead of 6n137?
Edit: the reason I’m asking is that I’ve seen several recommendations for 6n137 over 6n138, e.g. https://forum.mutable-instruments.net/t ... plers/5255

Happy (better) new year

I ordered the 8, as it seemed the most common. I will take a look at the 7. Thanks!

Edit: read the post. I will be ordering the 7, thanks!!