[sdiy] MIDI with +3.3V supply

[Seb Francis]

Neil Johnson wrote:
>
> Seb Francis wrote:
>> David Brown wrote:
>>
>>> It's worked on everything I've used it with.  Not a single problem.
>>
>> Good to know.  So it seems it's safe to work with the assumption that 
>> a MIDI input has 220R and 1.3V diode.
>
> Except you will have a problem now if you are being driven by Seb's 
> 3v3 MIDI output :)
>

Shouldn't make any difference surely?  Assuming all MIDI inputs are a 
standard 220R + 1.3V diode drop, then when driving with 3.3V one just 
uses smaller output resisters to maintain a 5mA current loop.  The 
receiving device should know the difference, the voltage it sees will 
still be 220R*5mA + 1.3V = 2.4V

Or are you talking about devices that are trying to run a uProc off the 
MIDI bus .. yes I agree these might not be happy .. but then these 
things are not operating to MIDI spec (they are drawing less current to 
try and get a higher voltage).

Seb