Converting sketches from 328 to 32U4? Grains to littleBits

Projects Programming
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I'm doing some synth/sound stuff and have a couple littleBits Arduino bits (32U4). Hoping to try some of the sketches meant for the Grains AE module which uses a 328. Since these processors are closely related, I'm guessing the main difference between the two are the in/out pin assignments, which would need to be changed in the sketch. Any other considerations to look out for or perhaps a quick guide in adapting sketches between Arduino models?

Here's links to the devices and sketches:

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The LittleBits products are fairly popular on ebay. I'd sell them and get the board for which the code is meant.

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That's not an option for me. I'm integrating the Arduino bit into a larger littleBits synth rig. Having to mess with breadboards, soldering or adding a different form factor defeats the convenience of going with littleBits platform. I'm trying to see how far I can take the littleBits stuff.

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Sounds like a cool project, have fun.

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At a glance the littleBits processor board uses normal IDE pin naming conventions.

I haven't looked at any sketch you may have linked to, but Imma guess it would have a good just of just working as long as you have the pins assigned to ones that the littleBits board makes available.

When I have a bigger window I will look at anything you've linked. Seems all straight ahead what Imdid see.

a7

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Thanks for chiming in. Yes, the littleBits Arduino bit is essentially a regular Leonardo. All the normal connectors seem to be there, just some use the littleBits snap connectors, while others are bare on the board.

I think the trick is that the Grains module seems to use a different pin names and it also looks like there are 3 analog CV inputs vs the 2 analog/1 digital on the littleBits connectors. I've never coded Arduino, so I'm not sure how to properly switch those assignments in the sketch. If I just try to upload a Grains sketch to the littleBits I get a "Compilation error: 'TCCR2A' was not declared in this scope."

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That register is one of the control registers for Timer2 on the 328P. It sounds like the 32u4 doesn’t have a Timer2 so you will have to move that function to a different timer. That will probably require using different output pins (the PWM outputs are driven by hardware timers)

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Ok that makes sense. I need to figure out the the 32U4's control registers and corresponding output pins that match the 328's functionality, then change those values in the sketch. Worth a try. Thanks.

1 Like
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Hi Davis, did you make any progress? I own a littlebits arduino synth myself and i think its a great idea, but new to arduino also.
Have a nice day, Jort

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It became a bit frustrating so I took a break. I'm planning on diving deep into it sometime this year as I now have 2 arduino bits.

I did however find a number of cool arduino sketches made for the bit that add additional synth functions:

  1. pitch quantizer/dual OSC trigger...so you can build a 2-OSC synth and also apply a scale to make more musical sequencers
  2. LFO/ADSR
  3. sample-based drum machine that uses preset patterns (doesn't send timing info to the sequencer though)
  4. USB-midi interface

I also started a littleBits synth group on facebook. Hopefully that can become a central place for this largely forgotten modular synth platform.

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Hi Davis, thanks for answering. Unfortunately i am not on facebook, but yes i like littlebits synt a lot. please report here if you if you make progres. Will check your recommendations.

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Hi Davis, couldnt this easily be solved by attaching bitsnaps to a diferent arduino, like an uno?
I am not that familiar with arduino.

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