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x0x Heart MIDI Interface (arduino/atmega)
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author x0x Heart MIDI Interface (arduino/atmega)
Starting a separate thread here to discuss progress on my MIDI interface for the x0x heart. All files are on Github and ideas, issues or pull requests are all very welcome.

A simpler version (around v0.1) works well to control everything except resonance. Now, I am working to add a digital pot to control resonance via MIDI. I looked at a scope and I think +/-5V should contain all signals at the dual 50k pot. The DS1267-050 is an economic DIP that will handle +/-5V. To create a -5V bias voltage for the digipot, I am using a 5V zener from -12V. Assuming the zener will handle .5W, max current would be .1A. The resistor drops 7V from -12 to -5. So the minimum resistor should be 70R. I'm calling it 100R to stay away from max rating of the zener. Is this a good way to get the -5V bias voltage for the DS1267? The datasheet doesn't mention current into the Vbias pin, but supply current is 650uA max.

BONUS: This uses every single pin on the Atmega328!
isn't the DS1276 obsolete? the Maxim website says its not available any more.
bare with me, i'm just a little confused. hmmm.....

Is this intended to work in conjuction with the voltages and inputs of the pacemaker pcb? Or would this effectively replace the necessity of the pacemaker pcb and make it so that the heart itself is midi controlled, instead of voltage controlled?

That being said, it looks like you have the voltage outputs as pwm outs, and do not have any filtering, etc. Are you happy with the voltage resolution and behavior? It's quite possible I'm missing something.
@av500 Yes, but there are plenty on ebay and I really don't want to use SMT. There are SMT versions available at Digikey if ebay runs out. I had to add the DIP14 package to the eagle library myself smile

@samuraipizzacat29 I haven't used a pacemaker, so I'm not sure how they would go together. I installed the x0x heart pots, but I marked the pot positions that enable full MIDI control and I prefer just using MIDI. Those control pins on the x0x heart are not CV - they are logic inputs. (The separate VCF cutoff CV is being generated with a DAC on my board.) The pacemaker generates PWM from your CV inputs. Here, I run the PWM above 20khz and the audio output is not affected. That said, if you sweep the MIDI controllers over the course of a note, you will often hear the 7bit value changing.
Yeah, that's why I'm confused, thanks. Though I'm still not excited about the pwm, I have two x0x-heart pcbs I plan to stuff (i'm a glutton for punishment) and then the midi interface might be superior for me.
Finally getting a chance to try this. Soldering this evening.

soooooo, is it working ? love
Gate/Pitch, Cutoff CV, Saw/Sqr, Glide and *MIDI RESONANCE* are definitely working. Still checking on other PWM controls - need to make sure of knob positions to test accent, etc.

That's right, MIDI controller 2 is controlling the resonance with the DS1267. I will program the "RES_POT" connected to the atmega to also control resonance and send MIDI controller 2 to the OUT/THRU MIDI port, so those messages could be recorded into a MIDI sequencer.
Software updated to v0.4: Everything tested is working, including control of resonance by either the "RES_POT" or MIDI controller #2. The only thing I haven't tested is the MIDI out/thru which should be sending controller #2 messages when the RES_POT is used to control the resonance.

Rockin' Banana!
awesome, looking forward to hearing some of the crazy things it can do.
Implemented a basic sysex patch dump. One can send a dump request, then store a 14-byte sysex patch dump that can be used to set all voice params at once.

MIDI Continuous Controllers can still be used to set voice params individually.
Hi jbeuckm,

this sounds like an awesome project! Did you finish it?

I'll try to build this following your files and source, and I was wondering about how the slide is implemented. Does it mean the x0x heart will only slide as long as CC65 is above 64? In other words there is no particular MIDI note legato the arduino would check if more than one note is held at any time, and if yes the slide would be activated? (I believe the MAM MB33 works like this, if I'm not mistaken)
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