Playing MIDI

[AstRii]

Hello,
I'm currently building my first DRSSTC and there are only few things remaining. And the thing i'm struggling with is the interrupter. I wonder how do you guys play MIDI files? I've seen interrupters which decode MIDI files in real time and create appropriate fixed on time square wave. Since now i've been using Arduino UNO as an Interrupter and the way i'm recreating songs on my DRSSTC is i think rather silly and inefficient. I'm using software AnthemScore to get all the notes from a song and then i manually write them into a text file (it's frequency and duration) which i'm then capable of playing. It takes me hours to recreate a single song. So i wonder, how do you play MIDI files on your DRSSTCs?
Thank you and happy new year!!:)

[davekni]

Others will reply with what's common - I think USB-to-MIDI, then to a real-time MIDI interrupter.

I'm working on a different path, learning the MIDI file format and writing an interpreter.  All the note frequency and timing is in the file, along with other things that can be ignored (skipped over).  I'll then convert the notes into an interrupter pulse waveform in MP3 format, record on a small MP3 player, and play it during performance.  This latter part is already running with a kludge input portion.

BTW, my existing kludge is to edit a MIDI file down to just melody (single note at a time), play it with a sine-wave synthesizer voice, record as .wav file, run custom code to detect rising zero-crossings and convert to pulses, then record as MP3.

[AstRii]

The real time MIDI to square wave interrupter is what i'm interested in. How is that achieved? Decoding the MIDI with python/C or something? Or is it just some hardware stuff?

[futurist]

You can download onetesla interrupter code from their website and use it with arduino uno/nano. MIDI to USB adapter isn't needed, if you adjust baud rate internal arduino ftdi chip can be used
http://onetesla.com/oneTesla_interrupter_firmware.zip

Try searching the forum, many people me including use this interrupter

[AstRii]

Is there any documentation for this code? My coding skills aren't any high level, so i don't fully understand the code and how to use it. Do i only need arduino for this? How do i send the MIDI data to the arduino? How do i change maximum on time? Which arduino pin is outputting the square wave to drive the optical transmitter? Sorry for those dumb questions:D

[Mads Barnkob]

I use a laptop with some kind of MIDI editor, doesn't matter which.

I got a collection of MIDI files edited to suit being played on a DRSSTC, you can find some here: https://highvoltageforum.net/index.php?topic=118.0

I use a cheap USB-MIDI interface from ebay to connect laptop to MIDI interrupter.

I gave up on spending time making my own interrupter, so I bought one from Loneoceans: https://www.loneoceans.com/labs/sales/midi2/ There is also a very good description on how it works.

[futurist]

Is there any documentation for this code? My coding skills aren't any high level, so i don't fully understand the code and how to use it. Do i only need arduino for this? How do i send the MIDI data to the arduino? How do i change maximum on time? Which arduino pin is outputting the square wave to drive the optical transmitter? Sorry for those dumb questions:D

It's actually very simple

You need to adjust baud rate to 38400 in midi.h line 56
on-time can be adjusted by changing LOOKUP_TABLE_SCALE prescaler in constants.h line 14, this is multiplied by on_times array, so for LOOKUP_TABLE_SCALE = 3, max. on-time would be 99 us

Pins, from schematics http://onetesla.com/media/wysiwyg/onetesla_interrupter_schematic.png

frequency pot is ADC0
on-time pot is ADC1
fixed/midi mode pin is digital 1
output pin is digital 0

On windows use this as Midi-serial converter - remember to set baud to 38400
http://projectgus.github.io/hairless-midiserial/

and this for the loopback interface
http://www.tobias-erichsen.de/software/loopmidi.html

loneoceans interrupter are actually two onetesla interrupters programmed to listen to different midi channel, but making your own is a lot more fun, and you learn something

[AstRii]

Ok thank you, that sounds pretty straight-forward. Though is there a need for the optocoupler between MIDI pin 4 and Arduino RX? What is it's purpose?

[Mads Barnkob]

Ok thank you, that sounds pretty straight-forward. Though is there a need for the optocoupler between MIDI pin 4 and Arduino RX? What is it's purpose?

There is a lot of EMI around a Tesla coil. The MIDI and USB interfaces are easily disturbed by this and all the cables running back and forth are good at picking up some noise aswell. It is always a good idea to add isolation between interfaces when we deal with Tesla coils

[futurist]

In your case you won't need optocoupler because you won't use USB to MIDI adapter but internal USB to serial converter used for programming arduino