[vcf-midatlantic] Any MIDI enthusiasts around?

RETRO Innovations go4retro at go4retro.com
Mon Mar 14 04:12:34 UTC 2022

On 3/13/2022 3:00 PM, ☼ wil lindsay ☼ wrote:
> Using an Arduino as a gate with some 6N138 optocouplers would allow 
> you to translate the signal from Midi to something like the 
> https://github.com/FastLED  Arduino-WS2810 libraries should be 
> fairly simple, give or take figuring out the power supplies for your 
> midi bridge and the LEDs.
Yeah, I already got the Arduino/AVR to LED thing done.  I also can 
easily do MIDI on the AVR, no problem.
> The only real issue in using MIDI would be the lack of match in the 
> specs. Midi is built around 0-127 (#0-#7F) where these LED libraries 
> are typically 0-255 for each color. I'm sure you could sort something 
> on the arduino like The Note (0-127) is an addressable LED and the 
> Velocity 0-127 (doubled) is the color, where notes would be expected 
> in a series of three. (R,G, & B).
If there is no standard per se, I'd like to keep it in a fashion where 
someone with a keyboard could easily control the lights manually, so the 
above looks good from note and velocity.  I think it might be better to 
use patch control msg to set to R, G, or B (or W), as then a manual 
player could then still play and control the LEDs directly.
> Midi also uses the irritating speed of 31,250baud which normally has 
> to be a cludge on an arduino.
Actually, 31250 is easy on the 16MHz Arduino/AVR (31250*16 = 500K, which 
is divisor 32 on the UART.  With the common crystals used on the AVR, 
9600 and such are the odd birds.
> It might make more sense to just use serial at a higher speed and 
> define your own information packets.
I could, for sure, but it seems like a project that does MIDI would have 
more appeal.
> The SPI speed of these LED strips is lightyears faster, and your  
> arduino code and/or the library will typically collect your color 
> commands in a buffer and send them a bit delayed. There's a little bit 
> of lag, but even if you're synching to music, the human brain has an 
> amazing tendency to make light flashing timing "feel" right, even when 
> it's off.

Yep, the MIDI speed is dwarfed by the SPI rate.

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