Can I bring the Daisy to its knees?

I’m in the final throes of building a synth with a 16-step sequencer (using a Daisy Seed for sound generation, of course!) and struggling to get all the processor hardware into my custom-built ceramic case. I’d like to get an opinion on whether it’s feasible to try replacing much of my current processor network with the Daisy.

Currently, I’m using 3 Arduino Nanos to process input controls (36 rotary encoders, 14 potentiometers, 22 3-way switches - most hardware attached to 7 GPIO boards communicating via i2c), feeding into a reduced footprint Arduino Mega which runs the sequencer, controls step LEDs, and generates Midi for the Daisy which is running a duophonic sound generator. The Mega also has an SD board attached for patch storage/retrieval and communicates with a NodeMCU running a Blynk controller to allow parameter display/update on an iPhone. What I’d really like is to replace the 6 processors with 2 - the Daisy and the NodeMCU. I/O pins are not an issue, I’d connect the daisy-chained GPIO boards via a single i2c port, have a serial connection to the NodeMCU, an SPI connection to the SD board, and two digital pins for LEDs. I’m concerned about processor load, however. There’s no way I could do all this processing on an AVR board (hence 4 of them), but the STM in Daisy is much more powerful. Is it worth trying to cram all this functionality onto the Daisy, or am I delusional? Thanks in advance for any insight!

@Elby, I am just now at a point in my learning curve where I can give you some insight.

As background, I have been fascinated with Hammond organs for years. I built a digital/analog “clonewheel” organ that used one Atmel processor per note of polyphony (I did six), and one more for keyboard and note processing. The processors were 20MHz single cycle 8/16-bit machines, but cost less than a buck. The six “tone generator” chips each output nine simultaneous sine waves as PDM (Pulse Density Modulation) bit streams. These note harmonics were filtered and summed externally with the other tone chips and scaled with “drawbar” pots. Very much hand-crafted assembly language programming, counting every cycle. It worked well but still wound up on the shelf.

Now the contrast: I am in the process of recreating a clonewheel organ on my Daisy as a processing power benchmark. I generate 96 simultaneous sine waves in semitone steps, accurate to Hammond’s tonewheel gear ratios. I process incoming MIDI notes with 16-way polyphony, switch their nine proper harmonic tones, and apply the drawbar settings to generate the output, all as the 48KHz sample rate. A little processor utilization blinking-LED routine (described elsewhere on the forum) shows that I am using about one quarter of the available horsepower so far!

As an added bonus, that functionality took a few days and a few dozen lines of code, once I got the damn toolchain set up and running right. The multi-micro software took weeks to code and fine-tune. Not to mention the time and effort to build the hardware.

So, the short answer is yes it is worth it, and no you are not delusional. :+1:

2 Likes

Nice. Once I finish my VA+FM synth a clone wheel was my next thought among a few others. Though I was thinking on going the “full polyphony” route where all 96 oscillators are running and using simulated bussbars / leakage etc - after all percussion is supposed to be monophonic etc :grinning:

1 Like

Thanks very much for the detailed answer and encouragement, Don. Your clonewheel sounds awesome! I’m starting to do some porting and experimenting. I’ll be sure to let folks know how it goes :grinning: