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Is Miniatmegatron open source?

Started by veryfungi, November 25, 2017, 03:17:56 PM

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They arrived after all. :)

I got these 10 pcb's for $5 delivered, in 5 days. Not kidding.

I'm still waiting for all the parts to come in. Making progress. Yay!


Ah yes - I've also had a few delivery issues over Xmas :(


Hey there Paul,

I'm putting this together and everything is working out well. I am almost ready to test it. Thought I'd share some photos of it. I'm hoping to get some cool sounds from this little project. :) The panel is laser plastic and I noticed the text is too dark in the upper box. I will fix it. I'll make an aluminum panel for it once my workshop is warmer.


I did the face plate over and adjusted the laser settings. I think I like the black better than faux aluminum. Next step is to install the program and start testing. I left off the components for the level shifting and will breadboard the amp first. After it's tested I will populate the board and solder them in. Do you have any input on the circuitry I asked about?


Looking really good! The mini uses the big cap as a cheap and easy way to remove the dc bias on the audio output. Considering Eurorack has dual power lines, I'd definitely recommend going to down the route of using the opamp to bias the audio properly.  However you won't need the cap before that stage, you'd want it at the output, along with a 1k resistor, as Eurorack has a standard of  1k output impedance.
Attached is the Oscitron output stage for your reference.  Very similar to yours apart from I derived the 2.5V using a voltage ref. Hope this helps!


Hi Paul, thanks so much!

Today I had set a side some time to test the little bugger. I was surprised about the hex file instead of a normal ino file. I expect it's due to some assembly language code inside the program. Unfortunately the guide I found online didn't work. It instructed me to turn on verbose when uploadig, looking at the actual command it uses and to replace the file locating of the hex file with your file. I used the command prompt, but there was an error, it could not fine a command at c: bla bla. Is there a better way? Thanks


You can download all the libraries:
and .ino:

or just use Easy Uploader and the .hex file.  It'll def work with any Arduino Uno. I assume you've installed the Arduino IDE which has the Uno drivers.
Click "show console" and copy and paste the error and I'll tell you the issue.


I'm sorry to bother you, this should be easy. I put "easy uploader arduino hex" into google and it laughs at me. I can not find anything called easy uploader. I followed the instructions here,

I was using admin command prompt, not power command, so I had to type it in perfectly, which I did, and it basically said windows does not recognize "C:\Arduino\hardware/tools/avr/bin/avrdude as a command. I do want to use the hex file because I am not a programmer at all.

I also don't know which of the two versions I should try. I used the only schematic I could find but now see there were two versions of the circuit board. I really appreciate your help.


Hi - just follow the instuctions on the Downloads page!  It's really easy and doesn't take long.  All downloads are on that page (Easy Uploader and the hexs)
Also a tutorial video here:


I'm such a nit wit, I never even thought to look for it on your website. Like duh...  :p

I got the code uploaded... It was, uh, easy. :) I now have a blue LED on the left and a green/red flashing led on the right. Yippy :D They are so bright! I need to swap out some resistors.

I used the version 2 of the code, not sure if it matters, and if it does, what it effects. I need to connect it to an amp and print the instructions, and have some fun. Thanks for again for your help!


hi Paul,

I was able to connect it to an amp and have some fun. Looks like the only thing I messed up is the direction on the A/B switch. I can fix that. I had the manual out and the quick start page. I was ready to test some specific items. :) I can't count the green blinks, or green and yellow, I can't do it. I also don't know if the items roll over or stop when they get to the min or max value. If it stops I should be able to click minus a bunch of times and know I'm at 0, then click + the number you want to select. If it wraps, or rolls over I don't know how to use it. I would much prefer a simple 7 segment display controlled by a shift register. I could wire up a shift register to a display, but I can't program these, so I guess I will keep trying. thanks


Quote from: veryfungi on January 21, 2018, 12:34:48 AM
I would much prefer a simple 7 segment display controlled by a shift register. I could wire up a shift register to a display, but I can't program these, so I guess I will keep trying. thanks

The main issue would be that the a shift register requires 3 data lines, but there's only 2 available for the value LED.  You could make use of pins 0 or 1 if you don't intend on using MIDI.  It would take some careful programming to make sure that the time taken shifting of data to the display didn't halt the playout of the sequencer.
Possibly a simpler alternative would be to put a MIDI connection on the front panel (using mini-jack wiring).  Then control it from an external MIDI controller, or even use the Touch OSC or Lemur templates for a graphical interface.  All parameters are available on MIDI CCs.