Sending ‘spectrum’ over I2C via A2 & A3

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    I have ordered a Lumazoid as part of a ‘lock down project’ – it has not yet arrived, but (of course) I’m very excited and thinking forward…

    With four strips of 120 LED which, the Lumazoid will deliver the same patter across all four but I’d like to see if I can get two of the strips to react to bass and two to react to full range.

    The cunning plan is to use the Lumazoid to do the sound processing and the full range strips but copy the spectrum[] over I2C to a second UNO just before analyzeAudioSamples() in the main loop, replicating all the required code on the second UNO for the bass.

    Two questions, if I may ask:

    1. Do you have a view on the feasibility of this


    2. Is there anything in the board design that would prevent the use of A2 and A3 for I2C?

    Many thanks for an excellent product and for open sourcing it.


    • This topic was modified 3 years, 6 months ago by Stutchbury. Reason: Typo in title

    Looking further into I2C on UNO and at the schematic, it would seem I may have better luck with SPI over JP2? Assuming I can use A2 or A3 for SS?


    Yeah, the problem with I2C is that the I2C pins (A4, A5) are not connected to any pads on the Lumazoid. SPI can work, as long as you know how to write an SPI slave on the other Arduino. Yes, you can use A2 or A3 for the SS pin.

    The Lumazoid code runs as fast as it can, sampling audio, performing the FFT, and then updating the LEDs. Now you will be also communicating data to the second Arduino, but SPI should be pretty fast, so it may not cause a performance issue. Give it a try!


    Thank you very much for your reply, Michael. My initial thoughts were to split everything after the ‘spectrum’ into two paths and run two separate sets of LEDs on the Lumazoid but thought it might be a bit too much for an UNO – hence the SPI (nee I2C) route. I could perhaps have two SPI slaves (A2 & A3), so the Lumazoid only does the sampling and FFT.
    I’ll test out via a standard UNO first – I’d like to not brick the Lumazoid!

    Many thanks & hope you are keeping safe.

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