[sdiy] Who apart from me things the whole MIDI board needs replacing ?

Roman Sowa modular at go2.pl
Thu Jan 27 13:48:21 CET 2022

But you can protect the input if you wanted to. Typicaly optos can take 
up to 50mA, but limiting to, say 20mA can be easily done with splitting 
this 220ohm resistor in half and putting 3V3 zener from there to GND.

As for detecting if it is MIDI or gate - if the pulse is longer than 
288us, let's say 400us as safe threshold, then treat it as GATE. And the 
other way around, if it was gate before, and then it sees all pulses 
shorteer than 400us a few times, then switch logic and treat it as MIDI.

I'm sure this would encourage a few people to put up a video why a 
module with such solution doesn't work, feeding it with very short 
pulses, but for normal use this should work.


W dniu 2022-01-27 o 13:25, Neil Johnson pisze:
> On Thu, 27 Jan 2022 at 12:10, Sean Ellis via Synth-diy
> <synth-diy at synth-diy.org> wrote:
>> Let me rephrase: in the circuit as shown will the MCU will get a signal no matter if it's a midi cable or a gate signal on a mono cable? Just seems like it would be easy to make a dual use input.
>>>> https://raw.githubusercontent.com/jakplugg/Neutron-Sound-Dust-of-Time/master/schematic.pdf
> Yes.... BUT... the gate signal source must limit the current to about
> 5 mA just as a MIDI transmitter would (e.g. +5V and two 220R
> resistors).
> So, you can't just feed it any old gate signal.
> And some way to tell the micro that the signal on the RXD pin is
> either MIDI _or_ Gate.
> Neil

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